text: A version of this procedure named for Tim Bartik multiplies ex-ante geographically disaggregated sectoral employment shares with aggregate sectoral employment changes to estimate labor demand shifts by geography over time.
full_question: A version of this procedure named for Tim Bartik multiplies ex-ante geographically disaggregated sectoral employment shares with aggregate sectoral employment changes to estimate labor demand shifts by geography over time. An attempt to use this technique failed because cities don't actually hire more police officers during election years. Since children born on different dates in the year are required to attend school for different lengths of time, another example of this technique used calendar date of birth to avoid selection bias in estimating the return to schooling. A prominent critique of this procedure is that it favors "cute," counter-intuitive results over addressing important questions that must be answered rigorously. For 10 points, name this identification strategy that pins down causality by using an exogenous covariate of a regressor to estimate the relationship between it and the outcome of interest.
first_sentence: A version of this procedure named for Tim Bartik multiplies ex-ante geographically disaggregated sectoral employment shares with aggregate sectoral employment changes to estimate labor demand shifts by geography over time.
raw_answer: instrumental variables [or IVs]