I stand corrected. It actual did grow from 1950 to 1971. However 3.2% on average is essentially nothing compared to the growth from 1869 to 1918. When the gdp went from a raw value from the chart of 4,500 to nearly 12,000 or nearly 266 percent or more than 6% a year over a forty year period. Please note I couldn't find the reference on the chart as to whether we were talking in terms of thousands of dollars or something else. Noe theless adding an equal number of zeros on to each value would not change the percentages in any case.