Early this morning, I was running on the treadmill and listening to an economics lecture by professor Timothy Taylor.
He said the year 1870 kicked off our modern era of economic growth. If you take the Gross Domestic Product (GDP), a measure of productivity, of the richest countries in the world in 1870 and compare them to the poorest countries, the ratio is 9:1.
By 1990 and the ratio widens to 45:1.