A quarter-century ago, small farms generated 46% of U.S. agricultural production. Today, the powerhouse of production is the large family farm with more than $1 million a year in gross cash farm income (GCFI). They represented 2.9% of the U.S. farm total in 2015 but were responsible for 42% of ag output, say USDA economists James MacDonald and Robert Hoppe.And the midpoint for cropland has moved from 589 to 1234 in the 30 years from 1982 to 2012.
Why is that? Illinois extension has interesting graphs, relating the cost of machinery per acre to the size of the farm; in other words the way increasing the land farmed spreads machinery costs over more land.
This has been true since farming began, and more so the more farmers invest in equipment.