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sergiocorreia / ivreghdfe

Run IV/2SLS with many levels of fixed effects (i.e. ivreg2+reghdfe)
MIT License
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Fixed effects by combination of variables and absorbed degrees of freedom #39

Closed YYecon87 closed 2 years ago

YYecon87 commented 2 years ago

I thank you for creating nice code, ivreghdfe! I encountered an issue regarding the usage of fixed effects by combining a subregion variable (137 different values) and decades (three different values). I created a variable of the subregion variable#decade. When I use regdhdfe, the absorbed degree of freedom is 137 multiply 3=411, but when I do with ivreghdfe, the absorbed degrees of freedom is 137 multiply 2=274. Also, the empirical results are the same when I use only two later (consecutive) decades. For the case of using two later decades, the absorbed degrees of freedom looks normal, 274. I am so confused. Would you help me to address this issue?

YYecon87 commented 2 years ago

Resolved! the instrumental variable data was empty for the first decade