The first step in understanding international income differences is measuring supplies of various factors of production and their productivity. Recent work suggests that these calculations should treat workers of different skill levels as imperfect substitutes. However, under this approach, it...

Using newly created data containing real output per worker, real physical capital per worker, and human capital per worker for US states from 1840 to 2000, Turner et. al (2007) analyze the growth rates of aggregate inputs and total factor productivity (TFP). We continue this line of work by...