Hi,

I am training to estimate the impact of one FTA on bilateral trade:


ppml_panel_sg TRADE FTA if exporter != importer, ex(exporter) im(importer) y(year) sym cluster(pairid)

However, I obtain this result:

note: FTA omitted because of collinearity over lhs>0 (creates possible existence issue)

Error: all main covariates appear to be collinear with the implied set of fixed effects
r(111);


what does it mean?



Thanks!