Did UberX reduce ambulance volume?

Ambulances are a vital part of emergency medical services. However, they come in single, high intervention form, which is at times unnecessary, resulting in excessive costs for patients and insurers. In this paper, we ask whether UberX's entry into a city caused substitution away from traditional ambulances for low-risk patients, reducing overall volume. Using a city-panel over-time and leverage that UberX enter markets sporadically over multiple years, we find that UberX entry reduced the per capita ambulance volume by at least 6.7%. Our result is robust to numerous specifications.