In 1900, about 40 percent of the population farmed. Today, it is closer to one percent. Throughout the better part of the 20 th century it was taken for granted that most people raised in the country would end up in the city. My father was the only one of nine siblings who stayed on the farm. There were many reasons why urbanization took place so quickly. Until the 1920s, agriculture expanded by putting more land into production. The years from 1920 to 1970, sometimes referred to as the “mechanization period,” saw technological advances fueled in large part by cheap and abundant fossil-fuel energy. Evermore efficient farm machinery along with pesticides, herbicides and synthetic fertilizer doubled and tripled production per acre and the average farm grew from 160 to many thousands of acres. From 1970 to the present, known as the “saturation period,” increasing energy input became subject to the law of diminishing returns. While we ...