Differentiated products demand systems are a workhorse for understanding the price effects
of mergers, the value of new goods, and the contribution of products to seller networks …

The Bartik instrument is formed by interacting local industry shares and national industry
growth rates. We show that the typical use of a Bartik instrument assumes a pooled …

We study the role of financial frictions and firm heterogeneity in determining the investment
channel of monetary policy. Empirically, we find that firms with low default risk—those with …

We study the welfare costs of markups in a dynamic model with heterogeneous firms and
endogenous markups. We provide aggregation results summarizing the macro implications …

We consider a linear panel event-study design in which unobserved confounds may be
related both to the outcome and to the policy variable of interest. We provide sufficient …

We study a Chinese policy that awards substantial tax cuts to firms with R&D investment
over a threshold or “notch.” Quasi-experimental variation and administrative tax data show a …

In this essay I discuss potential outcome and graphical approaches to causality, and their
relevance for empirical work in economics. I review some of the work on directed acyclic …

Real risk-free interest rates have trended down over the past 30 years. Puzzlingly in light of
this decline,(1) the return on private capital has remained stable or even increased, creating …

Problems involving causal inference have dogged at the heels of statistics since its earliest
days. Correlation does not imply causation, and yet causal conclusions drawn from a …

Demand elasticities and other features of demand are critical determinants of the answers to
most positive and normative questions about market power or the functioning of markets in …