Using a log-linear Taylor expansion of the multilateral resistance expression defined by Anderson and van Wincoop (2003), Baier and Bergstrand (2009) express the multilateral resistance by using the GDP-share-weighted average trade costs faced by the two hading partners relative to the GDP-share-weighted average of those trade costs between all the other countries. The MR term is thus a linear approximation of the MR between countries that allows capturing bilateral trade costs, such as distance or border, between countries relative to those of the rest of the world. This allows us, without introducing fixed effects, to identify the impact of each country-specific constraint on trade.