Putterman and Weil generously shared their whole data set with me – including a lot of info not available online.  I soon discovered two fun facts about ancestry-adjusted state and agricultural history.  Remember that state history is bounded from 0-1, agricultural history from 0-10.5.

Fact 1: The U.S. does better on both measures than the average country.

For ancestry-adjusted state history, the U.S. scores .57, versus .44 for the average country.

For ancestry-adjusted agriculture, the U.S. scores .59, versus .55 for the average country.

Qualitatively, of course, this is just what Garett has emphasized.  Quantitatively, though, it’s underwhelming.  Americans’ historical background is nothing special.

Fact 2: The U.S. does worse on both measures than the world as a whole.

The world’s most populous countries – China and India – both outscore the U.S. on both measures.  Which made me wonder: What happens if we weight countries’ scores by their populations?  Results:

For ancestry-adjusted state history, the U.S. scores .57, versus .62 for the world.

For ancestry-adjusted agriculture, the U.S. scores .59, versus .68 for the world.

Yes, by PW’s metrics, Americans come from subpar stock.  Deal with it.

Now consider: World GDP per capita is about $13,000; U.S. per capita GDP is around $53,000.  According to basic arithmetic, if everyone on Earth enjoyed current U.S. per-capita GDP, world GDP would roughly quadruple.

So what?  Taken literally, Putterman-Weil predicts that U.S. per-capita GDP would rise if the entire world population – warts and all – immigrated here.  World GDP would be more the four times its current height.  Personally, I think this is highly unlikely.  But if you prefer regressions over common sense, Michael “Double GDP” Clemens look like a pessimist.