This study documents how the demographics of new infections and mortality changed over time across US counties. We find that counties with a larger population share aged above 60 were hit harder initially in terms of both cases and mortality in March and April while counties with a larger...

Using county-level data on COVID-19 mortality and infections, along with county-level information on the adoption of non-pharmaceutical interventions (NPIs) in the United States, we examine how the speed of NPI adoption affected COVID-19 mortality. Our estimates suggest that advancing the date...

An important goal when analyzing the causal effect of a treatment on an outcome is to understand the mechanisms through which the treatment causally works. We define a causal mechanism effect of a treatment and the causal effect net of that mechanism using the potential outcomes framework. These...

This paper reviews methods that seek to draw causal inference from non-experimental data and shows how they can be applied to undertake ex-post evaluation of transport interventions. In particular, the paper discusses the underlying principles of techniques for treatment effect estimation with...