On amazon.com: Free to Choose: A Personal Statement (1980)
Excerpt: “The fecundity of freedom is demonstrated most dramatically and clearly in agriculture. When the Declaration of Independence was enacted, fewer than 3 million persons of European and African origin (i.e., omitting the native Indians) occupied a narrow fringe along the eastern coast. Agriculture was the main economic activity. It took nineteen out of twenty workers to feed the country’s inhabitants and provide a surplus for export in exchange for foreign goods. Today  it takes fewer than one out of twenty workers to feed the 220 million inhabitants and provide a surplus that makes the United States the largest single exporter of food in the world.”
2015: The percentage of workers in the USA in agriculture has fallen from ~5% in 1980 to below 1.5% today, while agriculture output continues to grow and there another 95 million people living in the USA.
Here is a video of Milton on the Phil Donohue show in 1979, asking “What is greed?”