In this paper we study methods for estimating causal effects in settings with panel data, where a subset of units are exposed to a treatment during a subset of periods, and the goal is estimating counterfactual (untreated) outcomes for the treated unit/period combinations. We develop a class of...

As technology platforms have created new markets and new ways of acquiring information, economists have come to play an increasingly central role in tech companies – tackling problems such as platform design, strategy, pricing, and policy. Over the past five years, hundreds of PhD economists...

In many prediction problems researchers have found that combinations of prediction methods (“ensembles”) perform better than individual methods. A simple example is random forests, which combines predictions from many regression trees.A striking, and substantially more complex, example is...

We present a new perspective on the Synthetic Control (SC) method as a weighted least squares regression estimator with time fixed effects and unit weights. This perspective suggests a generalization with two way (both unit and time) fixed effects, and both unit and time weights, which can be...

This paper analyzes the productivity of technology and job design in emergency response systems, or 911 systems.' During the 1990s, many 911 systems adopted Enhanced 911' (E911), where information technology is used to link automatic caller identification to a database of address and location...

This paper develops an alternative approach to the widely used Difference-In-Difference (DID) method for evaluating the effects of policy changes. In contrast to the standard approach, we introduce a nonlinear model that permits changes over time in the effect of unobservables (e.g., there may...

This paper studies the forces which determine how diversity at a firm evolves over time. We consider a dynamic model o a single firm with two levels of employees, the entry level and the upper level. In each period, the firm selects a subset of the entry-level workers for promotion to the upper...

In order to avoid competition, market leaders in platform markets often search for tactics that help them reduce multi-homing in the short run and thus deprive rivals of scale economies and network effects in the longer run. This paper considers a category of tactics that we refer to as...

This paper studies the forces which determine how diversity at a firm evolves over time. We consider a dynamic model of a single firm with two levels of employees, the entry level and the upper level. In each period, the firm selects a subset of the entry-level workers for promotion to the upper...

We study entry and bidding patterns in sealed bid and open auctions with heterogeneous bidders. Using data from U.S. Forest Service timber auctions, we document a set of systematic effects of auction format: sealed bid auctions attract more small bidders, shift the allocation towards these...