Less than a decade ago, China suffered from a bleak challenge: Not only was air pollution a recognized problem, but many didn’t trust the data being reported by local officials. The central government knew it needed to improve air quality, but that it would be impossible without knowing true pollution levels. The challenge was that local officials often prioritized economic growth and so had strong incentives to manipulate air pollution concentrations before reporting them to the central government.

So, the central government turned to technology. On the heels of declaring a “war on pollution,” the government installed an automatic pollution monitoring system throughout the country that collects pollution data from local stations, releases the data in real-time to the public, and critically is very difficult to tamper with. The move was one of a collection of measures the government took to reduce particulate pollution, which is now down 43 percent from before the war against pollution was declared.

Results from a new study now show that the increased transparency and improved data quality rooted out manipulation and led people to better protect themselves.

“This study demonstrates the critical role greater transparency and improved data quality played in China’s efforts to reduce the harms of air pollution,” says EPIC Director Michael Greenstone, an author of the study and the Milton Friedman Distinguished Service Professor in Economics. “Unpacking what is allowing China to win its war on air pollution is important in its own right but also very useful for other countries considering taking up this challenge against what our Air quality Life Index finds is the greatest current threat to public health on the planet..”

Comparing pollution data from before and after the installation of the technology, Greenstone and his co-authors found that the installation of automatic monitors significantly improved the quality of pollution data being reported. They discovered that reported particulate pollution concentrations increased by 37 percent immediately after the technology was installed, though satellite measurements indicated no change in true air quality before and after the installation. This suggests air pollution concentrations were being underreported by local government officials. The degree of underreporting was greater in heavily polluted and lower income cities.

When the reliable information on pollution was released, people appeared to respond by taking greater measures to protect themselves. Specifically, online searches for masks—a strong correlator for purchasing behaviors—increased by as much as 300 percent after the monitors were installed, according to the study. Searches for air filters increased by around 20 percent. The implication is that the manipulated data led people to have a false sense of security and insufficiently protect themselves from air pollution’s dangers. This finding underscores the human costs of inaccurate data, as well as the central role that people play in protecting themselves from air pollution.

“While the fight against air pollution continues to be an ongoing priority for the central government, the installation of automatic pollution monitors has played an important role in improving data quality, increasing compliance, and ultimately reducing pollution across the country,” says Guojun He, research director at EPIC China and a professor at the Hong Kong University of Science and Technology. “Along with government actions, an accurate picture of pollution has led more Chinese people to take important steps to protect their own health through the purchase of pollution masks and air filters. Surely, the monitors are a win-win.”

Greenstone and He co-authored the study with Ruixue Jia from the University of California San Diego and Tong Liu from the Hong Kong University of Science and Technology.