Price cap regulation and water quality

A number of studies suggest that price cap regulation may reduce the quality of the regulated good. This paper analyzes the impact on drinking water quality of a shift from cost-of-service to price cap regulation in Denmark, using a balanced panel of drinking water companies, for the period 2008 to 2016. The price cap was introduced in 2011 for companies above a certain threshold size. We exploit this quasi-experimental setting to estimate the impact of the shift in regulation using a regression discontinuity difference-in-differences approach. Our measure of drinking water quality is based on results from a compulsory surveillance drinking water testing program, which investigates whether or not water samples contain a level of microbiological content that exceeds limit values. More specifically, we compare the change over time in water quality for a treatment group of 113 companies regulated with price caps that have a size close to the threshold size for being regulated, with the change in drinking water quality for a control group of 282 companies that are below but close to the threshold size. We find that the shift in regulation has not caused a reduction in drinking water quality in Denmark.