Determinants of Urban Land Supply in the People's Republic of China: How Do Political Factors Matter?

This paper explores whether and how corruption and competition-for-promotion motives affect urban land supply in the People's Republic of China. Conditional on demand-side factors, we find that corruption is highly correlated with an increase in land supply. The corruption effects are strongest for commercial land, followed by residential land, and then industrial land. To shed light on the competition motives among prefectural leaders, we examine how the number of years in office affects land supply and distinguish among different hypotheses. Our empirical results show robust rising trends in land sales. These results are consistent with the hypothesis that among prefectural leaders the impatience and anxiety in later years from not being promoted may contribute to an increase in land sales revenue in later years. We also find that prefectural leaders may aim for more land sales revenue over their first few years in office instead of seeking higher revenue in their first 1–2 years.

posts and the Communist party has various effects. 3 The institutional background is that there are no specific term periods or limits for prefectural leaders; their appointments are reviewed and decided by provincial leaders within the Communist party. 4 The key criteria is local economic performance, measured in terms of gross domestic product (GDP) growth, and hence competition among prefectural leaders encourages them to sell land or pursue higher land sales revenue in order to fund infrastructure or other mega projects that may help boost the local economy. The fact that local governments were not allowed to borrow by issuing debt until very recently reinforced this incentive.
Based on these competition motives, we propose three hypotheses regarding how years in office may affect land supply. Hypothesis 1 is that a local leader tends to sell many land parcels or earn large land sales revenue in the beginning of his or her term in order to promote local economic growth. First, higher land sales revenue may provide more funds for infrastructure or mega projects that enhance economic performance. Second, even if land sales revenue is not used to fund infrastructure, the increase in land supply is conducive to economic growth because it lowers the cost of land for both business and manufacturing operations. It also lowers housing costs, which attracts larger population inflows. If Hypothesis 1 is true, land sales quantity and/or revenue tend to be larger in the initial years in office for prefectural leaders. Hypothesis 2 is that when a prefectural leader stays too long, compared with the distribution of years in office among prefectural leaders, he or she might feel pressure to perform and hence increase land sales, in terms of quantity and/or revenue, in order to increase the chance of getting promoted. Hypothesis 3 is also related to the later years of a prefectural leader's tenure. Hypothesis 2 assumes that when one is not promoted after staying in a prefecture for too long, he or she gets anxious for promotion. Another possible explanation is that he or she may simply "give up," and thus engage in fewer land sales for the purpose of getting promoted. Note that a prefectural leader might still increase land supply for the purpose of corruption. A priori, there are various possibilities regarding whether each hypothesis is supported by data. But logically, if there is any pattern in later years due to the competition-for-promotion motive, it cannot be that both Hypotheses 2 and 3 hold simultaneously.
At the same time, governments may supply more land simply because people need it; this response to demand pressure should be considered also. Thus, before probing the effects of political factors, we first determine whether standard urban-economic determinants have had an influence on urban land supply in the PRC. As in the Alonzo-Muth-Mills monocentric-city models and their variants, gains in population and income are two key sources of increases in land demand.
Our first set of results confirms that increments in both population and income significantly influence the change in land supply in positive ways.
Our next step is to study whether the two above-mentioned political factors possess additional significant influence on land supply, conditional on urban-economic determinants. In terms of corruption, direct evidence is hard to come by. Hence, we resort to the powerful finding of Cai, Henderson, and Zhang (2013) that the usage of two-stage auctions among the three methods of land sales by governments is an indication of corruption. 5 We find a very strong positive association between corruption and changes in land supply. This association is strongest for commercial land, followed by residential land, and then industrial land. We also run a set of regressions with land sales revenue as the dependent variable. We find that the effects of corruption on sales revenue for residential and commercial land are much smaller than the effects on the change in land supply, whereas the reduction of the effect for industrial land is relatively moderate. The contrast between these two sets of results show that the land sales revenue increases less than proportionally than the quantity of land sales. This, in turn, suggests that as corruption leads to local governments selling more land, they sell them at lower prices compared with other sales methods. Residential and commercial land seem to be the main sources of corruption.
The above results suggest that land sales revenue and quantity may entail different information. Therefore, in terms of the years-in-office effect, we also run two sets of regressions: one using the change in land supply and one using land sales revenue. Note that the leadership in the PRC is two track. At the prefectural level, the mayor is the official leader of the government, but the "real boss" is the highest party official in that prefecture, the party (chief) secretary. Thus, we run these regressions for both party secretaries and mayors to examine whether there is any difference between the two. To identify the years-in-office effect, we use a quadratic specification and tease out the specificity of prefectures and individual leaders by estimating prefecture-leader fixed effects. As the story is based on the political competition for promotion, we also control for corruption.
We find that there is a very robust rising trend. That is, the longer a prefectural leader is in office, the more land he or she sells, both in terms of quantity and revenue. The effect for party secretaries is much stronger than that for mayors. Here we only briefly sketch the reasons behind this rising pattern as details will be given in section III.C. First, the result is consistent with Hypothesis 2: impatience or anxiety at not getting promoted in later years may contribute to the rising trend. As 77% of party secretaries' length of term was not more than 4 years, those who stay longer than 4 years may feel anxiety or impatience.
Second, based on the results on corruption, a prefectural leader may increase land supply for more pocket money. Thus, if Hypothesis 3 is true and a prefectural leader "gives up" in later years, the rising pattern implies that these prefectural leaders become more corrupt in later years. However, we find that the effect of corruption on the increase of land supply decreases with the number of years in office. In addition, we also see that conditioned on other factors that may potentially affect corruption, the correlation between years in office and corruption are negative and insignificant. Thus, our results do not support Hypothesis 3.
Third, our results seem to contradict Hypothesis 1 because we do not see large initial land sales, but whether this is inconsistent with the competition-for-promotion motive or not needs to be carefully examined. As most cities in the PRC are growing in terms of both population and income during the review period, by restricting the quantity of land earlier, local government may raise more revenue later because land prices have been pushed up. Thus, an ambitious prefectural leader might trade revenue early in his or her term with higher overall land sales revenue over a longer time span, which may increase the chance of getting promoted (even a little later than the average number of years in office). If this conjecture is true, then there should be a rising trend in land prices. We find that this is indeed the case. We also find that the increases in land sales revenue are larger from year 2 through year 5, whereas the increases become smaller after 5 years. Thus, the rising pattern in the first few years may still be consistent with a competition-for-promotion motive because prefectural leaders may aim for higher land sales revenue overall in the first few (around 5) years in office.
We briefly review the related literature on the PRC's land market as follows. Although the surge of land and housing prices in cities in the PRC has attracted global interest (Wu, Gyourko, and Deng 2016;Fang et al. 2015), few attempts have been made to understand the urban land market from the supply perspective until very recently. While some research highlights the role of the central government's land use quota allocation system (Liang, Lu, and Zhang 2016), most existing literature focuses on local governments' land supply behavior. Based on empirical analyses of 35 major cities, Deng, Gyourko, and Wu (2012) point out that besides a strong common trend at the national level, local governments' land supply behavior is substantially affected by the size of budget deficits; local chief officers' desires for promotion also play an important role. Du and Peiser (2014) find that local governments intentionally control the land supply to maximize their revenue from the land market. Empirical research by Wu, Feng, and Li (2015) concludes that the budgetary deficits of local governments can affect their land supply behavior; increases in land prices, however, are mainly driven by demand-side factors. Their finding supports our assertion that urban-economic determinants such as income and population increases must be controlled before political factors can be investigated.
In comparison to the above-mentioned studies, we are the first to study the effect of years in office on land sales behavior. In addition, we also provide analysis covering all three major types of land usage instead of limiting the analysis to residential land parcels. In terms of corruption, whereas Cai, Henderson, and Zhang (2013) focus on the differential effects between two-stage and English auctions at the individual-parcel level, we focus on how this distinction affects prefectural aggregate variables.
The rest of the paper is organized as follows. In section II, we detail the basic sources of data and examine the standard urban-economic predictions, which is mainly a demand-side explanation. Section III explores whether and how various political factors matter, conditional on the demand factors. Section IV concludes.

A. Data
It is important to first clarify the level of geography used in our analysis. Most of the data we collect are at the prefecture level. The most common form of this level is the so-called prefectural-level city (di-ji-shi). Although direct-control cities (Beijing, Chongqing, Shanghai, and Tianjin) are politically at the same level of provinces, they are geographically similar to prefectural-level cities and hence included in this level. However, prefectural-level cities are usually too big, often much bigger than a metropolitan area in international standards based on commuting flows (Fujita et al. 2004). One can easily tell this by inspecting a map of, for example, Chongqing, Beijing, or Xuzhou. To remedy this problem, we use urban population, which is defined as residents of the urban areas in the prefecture, rather than the population of the entire prefecture. 6 Doing so means we look at all urban areas within a prefecture collectively; some of these urban areas may be outside the metropolitan area in which the prefectural government is located. Our prefectural population data is from censuses taken in 2000 and 2010. For the years in between, we either interpolate or extrapolate. We do not use the population data from the China City Statistical Yearbook because the population figures therein are only for the hukou (household registration) system; as such, they do not include migrant workers and do not reflect the true size of a city.
From the official website of the Ministry of Land and Resources, we collect information on all transactions of land parcels by various levels of local (urban) governments in the PRC. During the period 2007-2013, there were about 1.8 million land parcel transactions conducted by local governments. For the purpose of our research, we aggregate variables to the prefectural level. The change in the land supply measure that we use is the total floor space sold by governments in each prefecture in each year from 2007 to 2013. For some of our questions of study, government officials may care more about land revenue than increasing land supply. Thus, we also obtain data on land sales revenue. 7 We also know the type of land use per land transaction (residential, commercial, or industrial). From the revenue and quantity information on land sales, we calculate the average price per unit of land area or per unit of floor space. We also know the method by which land is sold. As mentioned in the introduction, the fraction of two-stage auctions is used to capture the degree of corruption. All land that has been sold in our data is urban land. This is because rural land is owned collectively by villagers and any rural land must be converted to urban land (via acquisition by the urban government) before it can be sold. Hence, our land sales data is consistent with the level of geography in our study.
From the China City Statistical Yearbook we also obtain other prefectural-level characteristics such as GDP and its breakdown. 8 In particular, we make the analysis consistent with our level of geography (all urban areas within a prefecture), we exclude the GDP of the primary sector and aggregate the GDP of the secondary and tertiary sectors to represent urban GDP (i.e., GDP produced in urban areas). Our population, land, and GDP data together cover 286 prefectural-level cities. The sources of other data are detailed in their respective sections or subsections.

B. Standard Predictions of Urban Economics
To start thinking about the determinants of urban land supply, imagine a strict version of the monocentric-city model: land and housing demand is inelastic. Suppose the city government's supply of land meets demand. Then one would expect a 45-degree line representing the relation between population increment and the change in land supply on a log scale. Figure 1 shows a scatter plot of population increment and change in land supply by prefecture on a log scale.
Although there is a strong correlation between the two variables, the slope is less than 45 degrees. This indicates that the increase in land supply is less than the increase in population. However, this is consistent with the predictions from a standard monocentric-city model when land and housing demand are elastic. That is, land demand grows less than proportionally with respect to population growth because new city residents are willing to reduce their consumption of land and housing to save on commuting costs. Standard models also predict that rising 7 Both land sales revenue and the change in land supply are used as dependent variables in our regression specifications. Du and Peiser (2014) make the point that local governments may want to hoard land to seek higher land sales revenue later. Hence, land sales revenues and changes in land supply might show different trends. Nevertheless, as we will see, these two do show different patterns in terms of corruption, but in terms of the years-in-office effect they often go the same way. See section III for more details. 8 The prefectural GDP per capita data used here are nominal. In the regressions that we run in the next section, we control for year fixed effects. Since monetary policy is the same economywide, we cannot control for year fixed effects if we deflate GDP per capita. incomes increase demand for residential land and housing, as well as land and housing for business and industrial activities.
Columns (1)-(4) of Table 1 show the regression results of the logarithms of the change in land supply-total and by type (residential, commercial, or industrial)-on the above-mentioned standard urban economic explanations of land-demand increases. In all the regressions in this paper, we control for year fixed effects and cluster standard errors at the province level. In the regression in Table 1, we do not include prefecture fixed effects because we want to investigate the effect of population growth. However, since our population data are either interpolated or extrapolated, the logarithms of population increments become constant over time. As industrial structures may affect the breakdown of land supply and potentially affect the total land supply as well, we use the ratio of tertiary industries to secondary industries (in GDP terms) to proxy industrial structure. Columns (5)-(8) show results when we control for this ratio.
As expected, the effect of population increments and the increase in GDP per capita are strongly significant. The elasticities of the change in land supply to population increase are around 0.42-0.48. The elasticities of the change in land supply to the increase in GDP per capita are around 0.04-0.07. The services-to-manufacturing ratio has a strongly significant negative impact on the change in industrial land supply. We also observe that this ratio has a positive effect on the change in commercial land supply; however, this effect is insignificant. As the two main sectors produce opposite effects, it is conceivable that the effect on the change in residential land supply would be insignificant. Finally, this ratio also has a significant negative effect on the change in total land supply, which indicates that  the effects on the change in industrial and residential land supply dominate that for commercial land supply.

III. How Do Political Factors Matter?
As verified in the previous section, increases in land supply may be due to government responses to demand factors such as increases in population or income. In this section, we study the effect of corruption and the years in office of prefectural leaders, conditional on the above-mentioned demand factors. Before we proceed, we first examine the relationship between land sales revenue and budget deficits.

A. Budget Deficits
There are institutional reasons that closely link land sales by local governments with budget deficits. Since reform of the tax-sharing system in 1994, the central government has kept a major part of tax revenues, while local governments remain burdened with increasing local expenditures. However, unlike local governments in advanced economies, local governments in the PRC were until very recently prevented from directly issuing debt to fund budget deficits or other investments such as mega projects. Accordingly, local governments in the PRC have relied heavily on land sale revenues as an important source of financing. Nominally, what we mean by deficit is the so-called "in-budget revenue" minus expenditure. Here, in-budget revenue includes tax and miscellaneous revenue, but not land sales. In 2007, aggregating over all prefectures, land sales revenue was 58% of total government expenditure. The corresponding percentages for years 2008-2013 are 22%, 37%, 50%, 44%, 34%, and 49%, respectively. These percentages indicate that land sales are indeed an important part of local government finances, although they vary substantially from year to year. The ratio of land sales revenue to government expenditure also varies substantially by prefecture. Figure 2 shows the distribution of this ratio; the unweighted mean and standard deviation are 0.35 and 0.15, respectively.
Not surprisingly, we also observe in Figure 3 a strong positive linkage between budget deficits and land sales. However, despite the positive and clear association between deficits and land sales, there is a great deal of variation in land sales for any given budget deficit. Needless to say, budget deficits are highly endogenous to various political factors and it is difficult to identify and disentangle all the relevant factors. For example, budget deficits may be higher because governments want to spend more on infrastructure to promote economic growth, which is related to the above-mentioned political competition motives. There may also be reasons other than political competition and corruption that influence budget deficits. To address this issue, in the regressions below we compare  the results when including budget deficits as a regressor to the results without including budget deficits as a regressor. The two sets of results are quite similar. In our benchmark regressions, we do not include budget deficits as a regressor. We also show results with this regressor in the robustness checks.

B. Corruption
Corruption is widely believed to be prevalent in the PRC, and land sales are often considered one of the main sources. However, direct evidence on corruption is hard to come by. Court, media, and party records reflect only part of corruption, and these records often reflect political rivalries and the (in)efficiency of the court system (or similarly, the inner control of the Communist party).
Nevertheless, Cai, Henderson, and Zhang (2013) provide indirect but powerful proof that corruption in land sales does exist via a comparison between different auction systems. They show strong evidence that among the three available methods of land sales (sealed bidding, English auction, two-stage auction), corruption is highly associated with the two-stage auction. The second stage of a two-stage auction is an English auction that occurs if more than one bidder is still competing for the land parcel at the end of the first stage. The key difference in a two-stage auction from an English auction is that the entry occurs sequentially in the first stage and is public information, whereas the entry to the English auction is simultaneous. The sequential nature of this auction form allows both government officials and developers room to signal one another, hence preventing additional competitors from entering. 9 Cai, Henderson, and Zhang (2013) show empirically that land sale prices and competition are significantly less for two-stage auctions and that officials divert coveted properties to two-stage auctions. These results are consistent with the theory of corruption and bidding that the authors develop. Given their results, we take the fraction of two-stage auctions among all land sales as a proxy for corruption.
Columns (1)-(4) in Table 2 show the results. Here, we regress the change in each type of land supply (in logarithmic form) on the fraction of two-stage auctions in that type, with the same set of controls in Table 1. Overall, a two-stage auction has a positive and significant effect on the increase of total land supply, as well as of each type of land. In Columns (5)-(8), we show the results when the dependent variable becomes the logarithm of land sales revenue. In comparison to the results based on quantity of land sales, the coefficients on corruption are dramatically reduced for residential and commercial land, whereas the reductions for total and industrial land are smaller. The effect on industrial land sales revenue becomes insignificant. Whereas corruption leads to a greater quantity of land sold, the increase in land revenue is less than proportional, suggesting that there is a price cut when there is a two-stage auction compared with other methods. The price cut is also evidenced in Cai, Henderson, and Zhang (2013), which is consistent with the "bribers' benefits." 10 These results suggest that residential and commercial land is a  major source of corruption. This is likely because residential and commercial land have much higher land prices than industrial land. 11 Is it possible that these regressions suffer from endogeneity issues? Generally, we cannot rule out the possibility, but we argue that this concern is likely to be minor. First, there could be a channel through which the increase in land supply leads to more corruption because of some sort of positive externality that spurs the development of the city and hence increases land demand, which gives room to more corruption via land sales. However, this channel is unlikely to be simultaneous with the channel from corruption to changes in land supply, as infrastructure takes time to build and mega projects such as special economic zones take time to realize. 12 Even when this time lag is short, the controls of current population and income alleviate this concern. However, can income and population themselves be endogenous via the same channel? Again, this is unlikely because of the time needed for the effect of land sales on GDP and population increases to take effect (e.g., migration restrictions in the PRC). Second, in terms of potential omitted variables, we do a robustness check by controlling for prefecture fixed effects. Here, we do not control for prefecture fixed effects because corruption may be highly related to local culture and tradition. We investigate prefectural fixed effects in section III.D.

C. The Effect of Years in Office
Here, we study how land sales revenue and the changes in land supply are affected by the number of years that a prefectural leader has been in office. This information about the trajectories of land sales, in terms of both quantity and revenue, within a prefectural leader's tenure, other things being equal, helps us test the three hypotheses described in the introduction.

Methodology and Results
In the PRC, the promotion of local government officials is determined by provincial-level party committees. Considering that for provincial-level party (chief) secretaries, the GDP growth rate serves as a key performance indicator in evaluating the performance of their subordinates (prefectural-level leaders), it has been widely believed that these prefectural-level leaders have a strong incentive to sales prices of more than 70% of two-stage auctions are at the reserve price, whereas this fraction is slightly more than 30% for English auctions. They also show that the price cut in two-stage auction is robust when conditional on other factors. This is in line with the bribers' benefit as they pay less to acquire land parcels using this method. 11 The mean, median, and 95th percentile of the prices of industrial land in our pooled sample are CNY200.2, CNY182, and CNY384.6 per square meter, respectively. The corresponding numbers for residential land are CNY574.2, CNY339.8, and CNY1,774.6; and those for commercial land are CNY605.9, CNY368.5, and CNY1,665.3. 12 A more complete modeling of this argument would require a dynamic model. boost local GDP growth, especially by investing in infrastructure and mega projects. Then, since a substantial amount of funding for such investments comes from land sales and since land sales are more flexible than other revenue sources, it is likely for local leaders to try to increase land sales revenue to support such development in infrastructure and mega projects. If land prices are very elastic, then selling more land entails more revenue, but if land prices are inelastic, restricting land supply may lead to higher revenue. In addition, local governments also have incentives to supply more land to accommodate growing urban populations, which of course is another important source of expanding GDP. Therefore, as land sales quantity and revenue renders different information, we include both as dependent variables.
To test the three hypotheses regarding the effect of years in office, we adopt a quadratic specification and run regressions for both prefectural party secretaries and mayors. As the conjecture is based on prefectural leaders' incentive to promote GDP, we control for both demand factors and corruption. Instead of simply controlling prefecture fixed effects to account for prefectural-level invariant factors, we control for prefecture-specific, party-secretary-mayor fixed effects. That is, for each prefecture, there is a coefficient for each prefectural leader to account for its specificity. In such a specification, the sum of such prefecture-leader fixed effects can be viewed as prefectural fixed effects. 13 For the demand factors, we can no longer use the population growth variable because the logarithm of population increase is time invariant, as we explained earlier in section II. But to avoid completely losing any information on population increases, we change the income variable (logarithm of the increase in urban GDP per capita) to GDP itself (logarithm of the increase in urban GDP). 14 From this point on, we do not repeat the word "urban" in the regression tables, as we focus on the urban areas throughout the entire paper.
Before discussing the results, we note that the endogeneity concerns are minor in this case as well. First, there is unlikely to be a reverse causality from land sales (in either quantity or revenue) on the years-in-office variable. The concern here is that land sales may come back to affect the increase in GDP. Again, this effect is unlikely to be simultaneous with the effect from years in office to land sales as it takes some time for the impacts of infrastructure and/or housing developments to be realized. Even when the time lag is short, in our robustness checks we show that the presence of the GDP-increase variable does not change the results. Last, the inclusion of prefecture-leader fixed effects should alleviate any concern on potential omitted variables. Table 3 shows the results for party secretaries. Columns (1)-(4) show the (logarithmic) results for the increase in land supply and Columns (5)-(8) show 13 An alternative way is to control for both prefecture fixed effects and prefecture-leader fixed effects. We find in this case the prefecture-leader fixed effects are less precisely estimated (i.e., larger p-values).
14 Because we are looking at increases, population information does not automatically drop out. those for land sales revenue. For all eight columns, we find strongly significant upward trends during the party secretaries' tenures. All quadratic-term coefficients are negative but insignificant, which suggests a very slight concavity in the rising trend. Table 4 shows the results for mayors. The increases in land supply also show significant rising trends with the exception of industrial land. The results on land revenue is much weaker, except that the coefficient for residential land remains significant. All linear-term coefficients for party secretaries are much larger than those for mayors. The coefficients of the controls are mostly insignificant, likely because the prefecture-leader fixed effects soak up much of the variations. In sum, we find a rising trend both in the quantity and revenue of land sales, and note that this pattern is much stronger for party secretaries than mayors.

Behind the Rising Pattern
Recalling the three hypotheses laid out in the introduction, Hypothesis 1 states that a local leader tends to sell many land parcels or earn higher land sales revenue in the beginning of his or her term in order to promote local economic growth. Hence, for prefectural leaders, land sales quantity and/or revenue tend to be greater in the initial years in office. Hypothesis 2 states that when a prefectural leader stays in the position for a long time, he or she might feel pressure to perform and hence increase land sales, in terms of quantity and/or revenue, to increase the chance of promotion. Hypothesis 3 states that when a prefectural leader is not promoted after being in the same position for an extended period, he or she may simply give up and engage in fewer land sales.
First, the rising pattern is consistent with Hypothesis 2; namely, impatience or anxiety at not being promoted in later years may contribute to the rising trend. To support this result, we collected data on the length of terms for prefectural party secretaries and mayors for all 1,773 party secretaries and 1,970 mayors in the 287 prefectural cities between 1983 and 2013. The average length of term for party secretaries was 3.6 years with a standard deviation of 1.9 years, and for mayors the average length of term was 3.3 years with a standard deviation of 1.8 years. Moreover, 77% of party secretaries' length of term was not more than 4 years, whereas the corresponding number for mayors was 70%. Our land and population data cover 7 years, but the longest length of term was 9 years for both party secretaries and mayors. (Some leaders were already in office in 2007 and stayed in that position throughout our data period.) As a large share of leaders stayed in office no more than 4 years, those who stayed more than 4 years may have felt anxiety or impatience.
The main difference between Hypotheses 2 and 3 is the different psychological reactions to not being promoted in later years. Based on the results on corruption, it is safe to say that a prefectural leader may increase land sales for more pocket money. Thus, if Hypothesis 3 is true and a prefectural leader gives up in Table 4 Notes: Data on the length of terms for prefectural party secretaries and mayors are from authors' collection. GDP data are from City Statistics Yearbook. Land data are from the website of the Ministry of Land and Resources. Standard errors are clustered at the province level and shown in parentheses. A prefecture (mayor) fixed effect is actually a prefecture-specific, mayor fixed effect; that is, for each prefecture, there is a coefficient for each prefectural mayor to account for its specificity. *** = p < .01, ** = p < .05, * = p < 0.1. Source: Authors' calculations.
later years, then the rising pattern in the years-in-office effect on land sales implies that these prefectural leaders become more corrupt over time. To check this, we examine the effect of interacting corruption with years in office in the regressions in Tables 3 and 4. As seen in Table 2, corruption exerts more influence on land sales quantity than land sales revenue for the reasons explained in section III.B; we examine the regressions with the change in land supply as the dependent variable.
The results are shown in Panel 1 of Table 5. Here we focus on the effect of party secretaries as the rising trend is most pronounced for them. For total, residential, and commercial land, the coefficients on the interaction terms imply that the effect of corruption on the increase of land supply is smaller the greater the number of years in office. 15 If a prefectural leader gives up in later years and becomes more corrupt, he or she should sell more land instead of less. Hence, the results here suggest that Hypothesis 3 is not supported. An alternative way to examine this is to run a regression of corruption on years in office and the same set of other regressors in Table 3. Here again we focus on party secretaries. The results are shown in Panel 2 of Table 5. We see that conditioned on other factors that may potentially affect corruption, the correlation between years in office and corruption is negative for residential land, positive for commercial land, and insignificant for industrial land.
Overall, there is a negative but insignificant correlation. We can conclude that the empirical results do not support Hypothesis 3. The rising pattern throughout the years in office implies that Hypothesis 1 is not supported, but whether this is inconsistent with the promotion-for-competition motive or not should be carefully examined. There are potentially two distinct arguments that may reconcile the competition-for-promotion motive with the fact that Hypothesis 1 does not hold. The first argument is that when urban areas expand cities need to convert rural land into urban land. However, rural land is owned collectively by rural residents. Therefore, even if a prefectural leader is ambitious, he or she may need to convert more rural land to urban land first before realizing his or her ambition. In the PRC, various uses of urban land are collectively called construction land, in contrast with land not slated for development. The increase in construction land can be used as a proxy for how much rural land is converted to urban land in a year. Focusing on party secretaries, Panel 1 of Table 6 shows the results when regressing the increase in construction land (in logarithmic form) on the same set of regressors as in Table 3. 16 Here, we do not find any significant effects for years in office. This suggests that the proportion of increase in construction land is roughly constant within a prefectural leader's tenure. Hence, if a prefectural leader 15 The coefficients on the interaction terms for industrial land are insignificant. The positive and significant coefficients of the quadratic interaction terms of the other types of land indicate a slight convexity, but as these coefficients are much smaller than those of the linear interaction terms, the overall pattern is still that the effect of corruption on the increase of land supply is less the greater the years in office. 16 Different columns show the variation when budget deficits are included and when the GDP-increase variable is excluded. See section III.D for the reasons behind these variations.   Determinants of Urban Land Supply in the PRC 173 Table 6.  Notes: Data on the length of terms for prefectural party secretaries and mayors are from authors' collection. GDP data are from City Statistics Yearbook. Land data are from the website of the Ministry of Land and Resources. Standard errors are clustered at the province level and shown in parentheses. All the regressions in this table are for party secretaries.
In the People's Republic of China, various uses of urban land are collectively called construction land in contrast with land that is not for development. *** = p < .01, ** = p < .05, is ambitious in land sales, we should probably see a larger increase in construction land initially, but we do not see this here.
The second argument is that as most cities in the PRC were growing in terms of both population and income during the review period, by restricting the quantity of land sales early a local government might raise more revenue later since land prices have been driven up. Thus, an ambitious prefectural leader might trade higher revenue early on in his or her tenure for larger overall land sales revenue over a longer time span, which could still increase the chance of getting promoted (even if a little later than the average number of years in office). If this conjecture is true, then we should expect to see a rising trend of land prices as well. Focusing on party secretaries, Panel 2 in Table 6 shows the results when regressing land prices (in logarithmic form) on the same set of regressors as in Table 3, except that we replace the GDP-increase variable with GDP itself. 17 Here we find that land prices rose over the years in office for the party secretaries (Column [1]) and that the effect is mainly driven by residential land prices (Column [2]). Further evidence for this argument comes from regressing land sales revenue on each nth year in office as a dummy (instead of the quadratic specification) with n = 1, 2, … , 9, and with the same set of other controls. Again, there is a clear rising trend in the effect of years in office, and the increments from one year to the next are 1.13, 1.15, 1.15, 1.23, 1.09, 1.05, 0.96, and 0.84, respectively. (The maximum number of years in office is 9 years for party secretaries; hence, there are eight increments). Thus, the increase in revenue is larger from year 2 to year 5, and the increase becomes smaller after 5 years. This is also consistent with the above-mentioned distribution of term lengths. Thus, we can conclude that the rising pattern in the first few years may still be consistent with the competition-for-promotion motive because prefectural leaders may aim for higher land sales revenue overall in the first few (around 5) years in office. 18

D. Robustness Checks
We conducted various robustness checks for our results in the previous two subsections. First, we conducted two sets of robustness checks for the results on corruption. For the reasons explained in section III.A, we ran the same set of regressions in Table 2 but are now controlling for budget deficits (in logarithmic form) in Table 7. The results remain quite similar to those in Table 2.
In the benchmark regressions in Table 2, we do not control for prefecture fixed effects, as corruption may be related to local culture. Table 8 shows the results  Table 7  with these prefecture fixed effects. Here, we see that the coefficients on corruption are reduced sharply, except that the coefficients on industrial land increases. Comparison with Table 2 suggests that corruption may indeed be related to local time-invariant factors but, even so, the increases in residential and commercial land supply still exhibit very strong correlations with corruption. Also intriguing is the fact that the effect of corruption on industrial land increases (and even becomes significant for industrial land revenue) compared with Table 2. This suggests that industrial activity is less correlated with local time-invariant factors, likely because industrial activities are quite mobile across locations. For the robustness checks for the years-in-office effect, we also examine cases where budget deficits are controlled. To address endogeneity issues, we rely on the assumption that the channel from land sales, in terms of either quantity or revenue, to boost GDP is not simultaneous; hence, we simply treat the currentyear increase in GDP as a demand factor variable. We also do a robustness check when GDP increase is not included in case the time lag of the above-mentioned channel is short. For these robustness checks, we focus on the total quantity and revenue of land sales. Table 9 shows the results for party secretaries. Columns (1)-(5) repeat the benchmark results from Table 3 for quantity and revenue of land sales, respectively. Columns (2)-(4) show the results for quantity of land sales with budget deficits controlled (Column [2]), when GDP-increase variable is not controlled (Column [3]), and a combination of the previous two cases (Column [4]). Columns (6)-(8) repeat the same cases for land sales revenue. The results are all very similar to the benchmark. Table 10 repeats the same exercises for mayors.
The rising trend for the increase in land supply remains quite robust. Again, we do not see much influence from controlling for budget deficits, but we start to see a rising trend for land revenue when GDP-increase variable is not controlled. In Table 9, we do not see such large changes in coefficients. This is likely because the explanatory power of mayors' years in office is weaker when compared with Tables 3 and 4; the GDP-increase variable accounts for some variation in land sales. Thus, when GDP-increase variable is taken out, mayors' years in office starts to capture the variations in land sales.
The last robustness check is to include prefecture-specific time trends. This is based on the following concern. Since land sales quantity, price, and revenue all rise over time, could our observed result of the rising trends for years in office simply result from the various controls not being able to fully explain these rising trends in terms of quantity, price, and sales? This concern is not fully addressed by controlling for year fixed effects, which capture overall rising trends in land sales quantity, price, and revenue, but not those specific to prefectures. Thus, we add prefecture-specific linear time trends to the regressions in Tables 3 and 4 and show  the results in Table 11 for total land supply only. Linear time trends translate to exponential time trends in levels as our dependent variables are all in logarithmic   Notes: Data on the length of terms for prefectural party secretaries and mayors are from authors' collection. GDP data are from City Statistics Yearbook. Land data are from the website of the Ministry of Land and Resources. Standard errors are clustered at the province level and shown in parentheses A prefecture-leader fixed effect is actually a prefecturespecific leader fixed effect, and a leader can be a party secretary or a mayor. That is, for each prefecture, there is a coefficient for each prefectural leader to account for its specificity.
form. Here, we see that even with the linear time trend, the rising trend in years in office remains quite robust. 19

IV. Conclusions
In this paper, we hypothesize that the two key features in the PRC's political economy of land supply are corruption and competition for promotion. We thus explore the effects of corruption on the increase in urban land supply, as well as the effect of prefectural leaders' years in office to shed light on the competition motives. Conditional on standard urban-economic (demand-side) determinants and industrial structure, the usage of two-stage auctions (as the indicator of corruption) is strongly associated with the quantity of land sales, but less so for land sales revenue. This suggests that while increased corruption leads to larger increases in land supply, it reduces prices compared with other methods of land sales. The effects of corruption are strongest for commercial land, followed by residential land. The effects for industrial land are insignificant. This indicates that industrial land sales are not a major source of corruption, perhaps because of its relatively lower land value.
For the years-in-office effect, we formulate three hypotheses regarding how the competition-for-promotion motive can matter. Our empirical results show very robust rising trends in land sales both in terms of quantity and revenue. These results are consistent with the hypothesis that the impatience and anxiety of not having been promoted may contribute to the increase in land sales revenue in later years, and are inconsistent with the hypothesis that prefectural leaders may give up in later years. By investigating how land prices and the increment of land sales revenue change with years in office, we find that the rising pattern in the first few years can still be consistent with the competition-for-promotion motive because prefectural leaders may aim for larger land sales revenue overall in the first few (around 5) years in office. Altogether, these results suggest that the competition-for-promotion motive is likely to affect land sales through a combination of maximizing overall revenues in the first few years in office by restraining early sales and the subsequent impatience or anxiety of not getting promoted in later years.
The questions that we ask and study in this paper seem quite specific to the PRC since these activities occur in an environment where local governments have dominant land ownership and strong control over land use, and where the selection of government officials is a top-down process rather than a bottom-up process as in a democracy. There are a few other communist countries that have similar features, but none of them is going through or has gone through the kind of economic reform and growth that has spurred urbanization in the PRC, except perhaps Viet Nam.
Hong Kong, China and Singapore also share some similar features in terms of the control over land use that these two governments have, but obviously there is a lack of political competition with other cities within a city's hierarchy.
Nevertheless, these lessons from the PRC are precious and interesting precisely because of their specificity as we get to see the effects of institutions. Although this paper provides no ground for making normative statements about the PRC's urban land supply, this first-cut evidence provides us with clues to think about normative issues. In particular, as the institutional environment seems to resemble one where Henry George's idea of a single tax on land might be put into effect, one can ask to what extent the Henry George theorem (Arnott and Stiglitz 1979) holds in the PRC. As mentioned by Cai, Henderson, and Zhang (2013), the prevalence of corruption has squandered the opportunity for the PRC to realize the ideals of Henry George. Our results indicate that corruption is relevant. Yet, the quantitative question remains unanswered here and the qualitative question of how political competition matters in terms of welfare must also be clarified. We tackle these questions in Hsu and Tang (2016).