I agree that Guns, Germs, and Steel is an excellent book, but it does not explain modern economical disparities. It basically explains why Europeans were the ones to conquer the African and American continents in the 15th and 16th centuries, and not the other way around (and the arguments are solid). But it clearly does not explain why modern countries have large economical disparities today, or why some countries colonized by Europeans are highly developed economically (e.g. the US, Australia) while others are not (e.g. Brazil, South Africa).

As for the article, I believe there is more to economical success than political institutions as well, it is such a complex process that it cannot be reduced to any single factor.