Fine piece. The top highlight above is on the money. America seemed to have these bursts when things happened so quickly. From 1912 to 1930, price of cars dropped by 63% while households that had access to a car went from 2% to 90% in the same period. We, of course, have Mr Henry Ford to thank for that.

As an aside — the total number of slaves actually taken to America from Africa and elsewhere was just under 400,000. Most slaves were born into slavery. But that 300% increase in 60 years looks rather high…