Quote from Mike805:
I think there's something critical missing from that statistic; the fact that the US has an order of magnitude larger population size than any other country in the top ten.
Large populations are inherently much more diffucult to govern effectively. New Zealand, for example, has 4.3 million people and new/creative financial/social systems can be implemented in relatively short time frames. The government in NZ can realistically determine the effects of new legislation in a matter of years as the implementation and result is immediate when compared to the US.
If we look at a country's path towards prosperity as a trial and error exercise, for every trial the US must spend much more time to determine the effectiveness.
The bigger the beast the slower it moves... but, it does get there, eventually.
Mike