American farmers were incredibly productive during this period. In the 1880s, only 15% of the land area of the United States was cultivated, but it is estimated that American farmers produced 30% of the grains of the world. The US was a vast exporter of farm products. In 1885, the US produced 500,000,000 bushels of wheat — of which Britain imported $175,000,000 worth of them. Their very success, however, created tremendous problems for farmers. At the heart of the problem was the fact that the yearly value of acre of the ten main crops dropped from $14.71 in 1870, to $9.71 in 1893. As a result many famers were forced into debt and were forced to mortgaged their farms. The end result was the slow, but steady, movement of farmers off the farm and into the cities. In the process many farmers became radicalized and supported populist candidates for political office.