Biases and barriers in rat reporting: Insights from Chicago’s 311 Data

Public reports of rat (Rattus spp.) sightings are often used to guide municipal rat management. However, to use these metrics to target areas of greater rat-associated risk, it is important to identify any potential sources of bias in reporting behavior. We surveyed residents to understand whether they are more or less likely to report rat sightings based on socio-demographic factors and perceptions of municipal rat management. We mailed surveys to random households in 12 neighborhoods across Chicago, a city with relatively high numbers of rat reports. Of the complete-case respondents (n = 384) who had all observed rats on their block, 38.8% reported their rat sightings. Respondents were significantly more likely to report their rat sightings if they saw rats more frequently, were older, owned rather than rented their home, and had moderate incomes compared to other respondents. Among complete-case respondents who did not report the rats they saw, the two most common reasons were 1) being unaware that they could report rats (43.1%), which was significantly more common for younger respondents, and 2) thinking that nothing would be done in response to their complaint (35.6%), which was significantly more common for respondents who saw rats more frequently. Our results show that many rat sightings go unreported and that rat reporting is not evenly distributed across demographic groups, which, in turn, has implications for quantifying rat distributions using these metrics. Municipal governments could address disproportionate reporting by engaging with younger residents in digital spaces and by advertising actions that will be taken following the report. Increasing the representativeness of rat reports will enable researchers and managers to better estimate trends in rat issues across space and time, identify contributing factors, and address the areas most in need of mitigation in cities worldwide.