Developed-world proponents of the “China Model” often point to environmental degradation as an example of the intractable sort of problem authoritarian governments, free of the need for grinding public debate, are good at addressing. But in new study examining one of the country’s highest profile environmental problems, a team of Chinese and U.S.-based economists casts some doubt on that thesis.

The subject of the the study, published by the National Bureau of Economic Research, is Beijing’s air quality, which changed markedly before and after the 2008 Olympics.

Beijing spent more than $10 billion to clean up its sometime spooky brown polluted air before the Olympics. According to the study, the government managed to improve air quality by 30% during the games, compared to year-earlier readings. But a year after the games, about 60% of those gains had evaporated.

What’s one to make of this? Like many others, the authors of the NBER study — Yuyu Chen and Guang Shi of Peking University, Ginger Zhe Jin of the University of Maryland and Naresh Kumar of the University of Iowa – give credit for the impressive improvement in air quality during the Olympics to China’s authoritarian system. Countries with such governments can make huge efforts to clear away problems when they are motivated to do so, they say.

The measures taken in what the authors describe as “the largest natural experiment in air cleaning” in Olympic history were indeed huge: Coal, steel and chemical plants were shuttered, vehicle traffic was reduced and auto-emission standards were increased.

There has been some suspicion Beijing cooked the books by prohibiting researchers from taking pollution readings at the site of the games and releasing only an official “daily air pollution index.” The researchers tried to compensate for that by examining pollution readings taken by National Aeronautics and Space Administration satellites which crossed China twice a day. The NASA readings generally confirmed what the Chinese government was reporting.

Why did the improvements dissipate so quickly? Again, the authors say, credit goes partly to China’s authoritarian political system. “Air quality improvement is a long time process and largely depends on the dynamic interplay of government policies and private compliance” –- in other words, the kind of action that a democracy can manage, once the society reaches a consensus for a cleaner environment.

Beijing’s efforts, by contrast, “were largely government-driven, much more intensive and implemented in a relatively short period,” they say. That may be characteristic of an authoritarian government which may have a “shorter-than-average time horizon than a democratic regime,” they write.

But developing-nation democracies don’t have much to boat about either. India, for instance, hasn’t managed to improve air quality despite high-profile efforts, according to studies the authors cite.

The economists recommend what economists always recommend – more research. As for Beijing, the air hasn’t been unusually awful lately. According to measurements reported hourly by the U.S. embassy, the air has generally been “unhealthy for sensitive groups,” with a few hourly readings of “very unhealthy” and one or two readings of “good.” Beijing residents may hope that continues, but they know from experience to expect that it won’t.