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From | Lucas <lucaselastic@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: 2-way Fixed Effects model |
Date | Wed, 5 Sep 2012 08:12:33 -0700 |
Thanks, I'll try it. FYI, my understanding is this is the dummy variable trap: 1) Y=b0 + b1 Male + b2 Female. If you dump b0 you can estimate: 2) Y=b1 Male + b2 Female But, you still can't estimate: 3) Y=b1 Male + b2 Female + b3 White + b4 Nonwhite Equation 3 reflects the dummy variable trap. Sam On Wed, Sep 5, 2012 at 1:03 AM, Ulrich Kohler <kohler@wzb.eu> wrote: > Another way would be > > . iis company > . xtreg y x* i.county, fe > . predict u, u > > Variable u then holds the coefficients of the dummy-variables for > company centered at their mean. Note that this is just another way to > access the dummy variable coefs. Austins remark concerning the > reliability of the coefs remains to be true, therefore. > > I don't know waht the "dummy variable trap" is. > > Uli > > Am Dienstag, den 04.09.2012, 17:19 -0700 schrieb Lucas: >> Austin, >> >> Thanks for your note. I know I can do this for a one-way OLS fixed >> effects model with the -noconstant- option. However, in a two-way >> fixed effects model this should produce a dummy variable. That's what >> I expect with the reg command. Am I mistaken? Also, does the iv2reg >> prevent the dummy variable trap? >> >> Sam >> >> On Tue, Sep 4, 2012 at 10:13 AM, Austin Nichols <austinnichols@gmail.com> wrote: >> > Lucas <lucaselastic@gmail.com> : >> > Just use -regress- e.g. >> > reg y x* i.company i.county >> > but you will need many obs per company-cluster pair to trust those coefs. >> > >> > Also see -ivreg2- on SSC for one implementation of 2-way cluster-robust SE >> > [ http://www.stata.com/meeting/boston10/boston10_baum.pdf ] >> > and compare SEs on x vars (not SE on fixed effects) >> > using OIM, het-robust, and cluster-robust SEs. >> > >> > On Tue, Sep 4, 2012 at 1:02 PM, Lucas <lucaselastic@gmail.com> wrote: >> >> Dear Statalisters, >> >> >> >> I thought this was a simple issue, estimating a 2-way fixed effects >> >> model, but, alas, I cannot figure it out. I see several stata and >> >> user-written commands, but I am not certain any of them will work in >> >> my situation. >> >> >> >> My data is that I have dozens of companies crossed with dozens of >> >> jurisdictions (e.g., counties). For substantive reasons I need to >> >> obtain the coefficients for each company and for each county (which >> >> makes areg not quite what I need). >> >> >> >> FYI, there is no time element here, so lags, AR processes, and such >> >> are not relevant. >> >> >> >> Any guidance anyone can offer is greatly appreciated. >> >> >> >> Sam >> > * >> > * For searches and help try: >> > * http://www.stata.com/help.cgi?search >> > * http://www.stata.com/support/statalist/faq >> > * http://www.ats.ucla.edu/stat/stata/ >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/statalist/faq >> * http://www.ats.ucla.edu/stat/stata/ > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/