But this is how innovation works. First, we make new things, and then we make those things cheaper. The price and size of tractors fell rapidly over the next decade. Introduced in 1917, Henry Ford's smaller, cheaper "Fordson" was the iPad of tractors: the definitive, consumer-friendly genre-busting technology that immediately dominated a formerly desolate market. Round after round of new technologies -- power lifts, rubber tires, diesel engines -- eventually established a dominant model that made the 1940s the decade of the tractor.



That decade spelled the end of the farm horse. One tractor could replace about the pulling-power of five horses or mules, agricultural historian Bruce L. Gardner wrote in his book American Agriculture in the Twentieth Century. Richard H. Steckel and William J. White produce this epic graph which plots the accelerating rise of tractors and the decline of horses through the 1950s.



When a technology comes along that threatens an American worker, the solution is to have the worker work harder. This idea is central to the Great Speedup thesis from Monika Bauerlein and Clara Jeffery in Mother Jones. Amazingly, or perhaps predictably, it was the same with 1930s horses. A 1935 economic paper published in the The American Economic Review titled "Tractor Versus Horse as a Source of Farmpower" noted that the only way in which horses could outperform tractors was if you worked them day and night to exhaustion:



Where horses are used little during the year, tractor power frequently is cheaper than horse power, even if prices of feed and horses are relatively lower than the prices of fuel and tractors. The reverse situation often occurs where the annual work per horse is large. Thus, the annual work per horse becomes a more important factor than the relation of the cost of feed and horses to the cost of fuel and tractors. The saving on labor which can be made by operating tractors instead of horses is significant in inducing farmers to shift to tractor power.



It would be churlish to suggest that the most important consequence of the tractor was the elimination of farm horse jobs. But one of the key ways that technology makes our lives cheaper is that it replaces the workers required to do a certain task. That's exactly what tractors did to horses. It's also what tractors did to people.



THE ROBOT FARM



You probably don't think about tractors very often. I sure don't. But that's just a sign that the tractor is doing its job.



The mechanization of agriculture (which was catalyzed by, but not confined to, the tractor) means we need fewer farmers to make more food every year. That has freed up people to work on the other stuff we care about, like consulting, and teaching yoga, and researching tractors.



In 1910, one third of our 92 million citizens and 38 million workers were on the farm. By 1950, only 10% of Americans worked on farms. By 2010, farmers accounted for only 2% of the workforce, even though we produce and export considerably more food. Machines took over the farm.

