Investment in transport infrastructure improves a mainland mayor's chances of promotion, while spending on environmental improvements lowers them, a research paper using data between 2000 and 2009 has found. The paper, written by a Chinese, Singapore and Canadian academics for the US nonprofit National Bureau of Economic Research, said building roads, railways and airports correlated strongly with gross domestic product growth, land prices - a major source of government revenue - and city-level cadres' odds of promotion. In contrast, building environmental infrastructure adversely affected their careers. With other factors remaining unchanged, when investment in environmental infrastructure increased by one standard deviation it lowered the probability of promotion by 8.5 percentage points for cities' party chiefs and 6.3 percentage points for mayors, the paper said. "Spending on transportation infrastructure immediately creates economic activity, and thus might have a more immediate and tangible impact on economic growth than would spending on environmental improvements," it said. The paper warned that if China's top leadership really wanted to improve the environment, it had to include measurable and tangible evidence of progress towards environmental goals in formulae determining lower-level cadres' promotions and budgets. Sheng Guangyao, a researcher at the Chinese Academy of Social Sciences' Institute for Urban and Environmental Studies, said in an interview with the Post earlier this month that as long as the performance of officials was assessed in this way, local governments would devote more resources to transportation than the environment. Because officials in higher-level governments, not the people, had the final say on judging a mayor's performance, they tended to focus on projects that were more easily seen and achieved results sooner, such as roads, Sheng said. Besides, he added, "once a mayor takes office, the first thing he is concerned about is always fiscal revenue and spending, and selling land is the most important source of revenue." Yuan Chongfa , the deputy director of the China City Development Academy, told the Post recently that transport infrastructure, especially in some inter-city projects, could bring direct profits by pushing up real estate prices. "Every mayor will consider how much money a project can bring to the government," he said. Many pollution treatment projects, however, were more complicated, given that they often required co-operation with nearby cities, and the results could not be observed until many years later. The paper said that city-level "environmentalists" - green-minded officials - might offend province-level cadres whose promotions had been more clearly driven by economic growth, therefore affecting their own career prospects. Another possibility was that city-level cadres with less hope for promotion or who were less career-minded were more likely to invest in environmental improvements, it said. Professor Peng Zhenhuai, a public policy specialist at Renmin University, told the Post earlier this month that many medium-sized cities attached too much importance to transport. "Many cities are proud of owning an airport, like Zhuhai, whose economy has been dragged down by the airport," he said. The airport, which was built in 1995 and has been jointly managed by the Hong Kong Airport Authority since 2006, had low passenger and freight traffic and survived by staging an annual air show, he said. About 20 cities in the area where Jiangsu , Anhui , Henan and Shandong provinces intersect had an airport, Peng said, with an average distance between any two airports of just 100 kilometres. "This is totally unnecessary and a waste of resources," he said.