An event study is an empirical method designed to measure the causal effect of a precisely dated event on a variable of interest, by comparing the observed path of that variable around the event with the path it would have followed in its absence. It relies on the unambiguous identification of the event date, the definition of an observation window encompassing that date, and the construction of a Counterfactual – ‘normal’ behaviour estimated over a reference period or observed in an unaffected group.
