Exercise 6 (+additional question) in Mankiw:

The country dummies is to be included to allow for country-specific fixed effects- In contrast to the cross2007.xls, paneldata.xls contains no values on I, G, P, Open for the year 2004. In regressions where these variables are included as explanatory variables use the initial values on I , G and Open as explanatory variables. ................
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