“We can go back to organic agriculture in this country if we must—we once farmed that way 75 years ago. We know how to do it. However, before we move in that direction, someone must decide which 50 millions of our people will starve.” –Earl Butz, USDA Secretary of Agriculture, 1971.

It’s the most emotionally powerful argument that’s ever been made against organic farming: Organic methods can’t feed the world. Many agronomists believe that it is their moral responsibility to use chemicals to keep people from starving. But where do they get their numbers from?

Like most other opponents of organic farming, Earl Butz assumed that organic farming is identical to early twentieth-century American farming methods. It was widely stated in the 1940s that it took 2.5 acres of land to feed one person using those farming methods. There were about 375 million acres of arable land in the United States in 1970. 375 million divided by 2.5 equals 150 million. The US population was about 200 million. So Butz calculated that the extra 50 million people would have to starve if the nation went back to 1920s “organic methods.” A powerful argument, right?

Wrong. Butz’s math was right, but his value of 2.5 acres of land per person wasn’t. Nobody was very good at citing where they got that number from, but I finally traced it back to an obscure 1935 USDA study titled Agricultural Land Requirements and Resources: Part III of the Report on Land Planning. This study calculated agricultural land use by capita by dividing the number of acres of agricultural land by the number of Americans.

The conclusion? In the 1930s it took 2.3 acres of land to feed each American. That is, of course, a bit lower than 2.5—only 37 million people would starve, Secretary Butz! But after reporting these results, the authors mentioned something else—16-22% of that land was used to feed the horses and mules used in agriculture. The amount that would be required if tractors were used on most farms (like they were in 1970), was only 1.8 acres per person. So if farmers in the US would have gone back to 1930s cropping systems in 1970 but still used tractors instead of horses, there would have been enough food to feed 208 million people.

Of course, what Butz and his colleagues failed to realize was that modern organic farming has much higher yields than typical 1930s American farming. Organic farmers, like their conventional counterparts, have the advantage of improved crop varieties, closer row spacing, irrigation, conservation tillage, and other methods that contributed to the postwar rise in crop yields. Remember that there was a terrible drought and the Dust Bowl in the 1930s—a lot of arable land wasn’t producing crops at all during that decade. With careful attention to building soil fertility and organic matter, modern organic farmers have yields equal to or sometimes better than conventional farmers, especially in drought years.

But even if organic farming was equivalent to 1930s agriculture, Butz was wrong about how many people it would feed. Unfortunately, none of the people who wanted to believe him bothered to check where he got his numbers from. The lesson for today? Always trace any seemingly shocking statistics back to their original source. You just might be surprised.