Cameras on every corner appear to deter crime. Chinese cities that installed denser surveillance networks between 2014 and 2019 saw significantly steeper declines in crime, especially crimes committed in public view.
The study is by Hong Ma of Tsinghua University and Mingzhi Xu, Wei You and Jinmei Feng of Peking University. It appears in the January 2026 issue of the Journal of Development Economics.
Measuring the world’s largest camera build-out
China’s Skynet, Smart Cities and Sharp Eyes projects aimed to build the world’s largest surveillance network. In an earlier draft, the authors report that by 2019 the government had installed more than 200 million cameras and had spent 76.9 billion yuan, about $11.3 billion, on cameras and related equipment.
To measure crime, the team ran text analysis on court judgments published in the China Judgements Online database, sorting cases by type and counting them by city and year. To measure camera density, they analyzed government procurement contracts for surveillance cameras.
The analysis covers 322 prefecture-level cities. These are large units, averaging 3.93 million residents in 2010, which limits the worry that criminals simply moved to unwatched areas nearby.
Cities that buy more cameras may differ in other ways, so the authors used an instrument. They took the number of camera manufacturers in each city before 2010 as a predictor of how cheaply and heavily local governments could install cameras later.
Where the cameras made a difference
In the draft version, the baseline estimate was that doubling per capita camera investment cut the crime rate by 10%. The result held across alternative crime data, measures of camera investment and placebo tests.
The drop was larger for crimes that happen in public view, such as drug offenses, robbery, theft, fraud, extortion, public security offenses and violence. Descriptive trends showed no comparable fall for prostitution, gambling, counterfeiting or bribery, which cameras find harder to catch.
The draft also reports larger effects in cities with more migrants and minority residents, stronger gender imbalances and weaker economies.
Feeling safer, working longer
The authors linked their data to national household surveys. People in more heavily surveilled cities reported more satisfaction with the government and a greater sense of security.
That sense of security was associated with longer working hours. The draft found the gains in security, satisfaction and hours were especially large for women.
A back-of-envelope calculation in the published abstract puts the cost of preventing one crime at about $6,373, which the authors call highly cost-effective.
There are diminishing returns, though. In the draft, the marginal cost of preventing an additional crime tripled as a city’s network grew from the 5th to the 30th percentile of camera density.
Study Details:
- Title: Keeping an eye on the villain: Assessing the impact of surveillance cameras on crime
- Authors: Hong Ma, Mingzhi Xu, Wei You, Jinmei Feng
- Journal: Journal of Development Economics, Volume 178
- Publication Date: January 2026
- DOI: 10.1016/j.jdeveco.2025.103557