<a href="http://www.economist.com/world/international/displaystory.cfm?story_id=15328727" rel="nofollow">http://www.economist.com/world/international/displaystory.cf...</a> has an interesting chart too, covering just the past decade or so but comparing a few developed countries.<p>The Economist uses OECD data, which comes in somewhat lower than the data cited by the parent. I would be interested in knowing the reason for the difference between these numbers.