What is behind the Productivity index

There is a interesting comment in NYtimes Prof. Paul Krugman(won the Novel Prize for Economics 2008)said that the index of productivity of USA is better than France. But behind this index there is a difference of life style between the two. French people are usually enjoy long vacation and leisure. So people should know this life-style difference. But on the other hand Japan's index is worse than France.What makes worse? Japanese productivity is not good without long vacation and leisure. Why??
http://krugman.blogs.nytimes.com/2011/01/28/gdp-per-capita-here-and-there/