 Same Root Different Leaves: Time Series and Cross‐Sectional Methods in Panel DataDennis Shen, Peng Ding, Jasjeet Sekhon and Bin Yu Econometrica, 2023, vol. 91, issue 6, 2125-2154 Abstract: One dominant approach to evaluate the causal effect of a treatment is through panel data analysis, whereby the behaviors of multiple units are observed over time. The information across time and units motivates two general approaches: (i) horizontal regression (i.e., unconfoundedness), which exploits time series patterns, and (ii) vertical regression (e.g., synthetic controls), which exploits cross‐sectional patterns. Conventional wisdom often considers the two approaches to be different. We establish this position to be partly false for estimation but generally true for inference. In the absence of any assumptions, we show that both approaches yield algebraically equivalent point estimates for several standard estimators. However, the source of randomness assumed by each approach leads to a distinct estimand and quantification of uncertainty even for the same point estimate. This emphasizes that researchers should carefully consider where the randomness stems from in their data, as it has direct implications for the accuracy of inference. Date: 2023 Downloads: (external link) Related works: Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text Persistent link: https://EconPapers.repec.org/RePEc:wly:emetrp:v:91:y:2023:i:6:p:2125-2154 Ordering information: This journal article can be ordered from Access Statistics for this article Econometrica is currently edited by Guido W. Imbens More articles in Econometrica from Econometric Society Contact information at EDIRC. |
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