Max-Share Misidentification. (Joint with Paul Ho and Thomas A. Lubik.) 

Max-share identification relies on a decomposition of the forecast error variance (FEV) over a target horizon. Consequently, it often conflates multiple shocks because the contribution to the FEV depends on the impulse responses at untargeted horizons and the shapes of the responses to untargeted shocks. We alleviate the issues using a so-called "single horizon" alternative that focuses narrowly on the actual target horizon. We characterize the identified shock in terms of true structural shocks in the single horizon problem and show that this typically bounds results in the literature's usual implementation. Using a numerical demand and supply example and an empirical news shock application, we show that the traditional max-share approach inadvertently places weight on untargeted transitory shocks, a problem that the single horizon approach avoids.

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  ]