Max-Share Misidentification. (Joint with Paul Ho and Thomas A. Lubik.) [Online Appendix | FRB Richmond Working Paper No. 25-02]

While max-share identification has become increasingly popular in a wide range of applications, we show that its validity requires necessary and sufficient conditions that are rarely satisfied in practice—the target variable’s response to the target shock must be (i) orthogonal to its responses to untargeted shocks and (ii) larger than combinations of those responses. Imposing additional restrictions on the target shock weakens but does not fully eliminate these conditions. We show that in practice, the weight max-share places on an identified untargeted shock can be obtained by projecting the response to that shock on the max-share response. We also theoretically characterize consequences of local and global violations to the identification conditions. Empirically, the TFP news and main business cycle shocks identified by Kurmann and Sims (2021) and Angeletos et al. (2020) are, respectively, at least a third and a quarter contaminated.

Quantifying Delay Propagation in Airline Networks. (Joint with Jakub Kastl and John Lazarev.) 

We develop a framework for quantifying delay propagation in airline networks. Using a large comprehensive data set on actual delays and a model-selection algorithm (elastic net) we estimate a weighted directed graph of delay propagation for each major airline in the US. We use these estimates to decompose the airline performance into "luck" and "ability." We further use these estimates to describe how network topology and other airline network characteristics (such as aircraft fleet heterogeneity) affect the expected delays. Finally, we propose a model of aircraft scheduler who allocates effort to minimize costs of delay on a network and show how the effort cost can be estimated. We then use the estimated effort cost to evaluate counterfactual scenarios of investments in airport infrastructure in terms of their impact on delays.

Trial and Error in Influential Social Networks. In Proceedings of the 19th ACM SIGKDD Conference on Knowledge, Discovery, and Data Mining (KDD), ed. by Inderjit S. Dhillon et al., ACM (2013), 1016-1024. (Joint with Ning Chen, Xiaohui Bei, Xiangru Huang and Ruixin Qiang.) [ DOI | .pdf  ]

What Drives Business Cycles? (Joint with Paul Ho and Thomas A. Lubik.)

FRB Richmond Economic Brief, October 2025, No. 25-37