Chicken is the most commonly eaten animal in this country, surpassing beef or pork. And with dietary recommendations that Americans eat less red meat, the obsession with chicken—which has lasted more than 30 years already—shows no sign of stopping.

Maintaining that appetite, though, is already pushing the bounds of what's biologically possible—and perhaps what's humane.

To get a sense of how many more chicken Americans are eating compared to before, take a look at the chart below. The average American eats more than four times as much chicken today as he or she did in the early 1900s, according to data from the USDA. Currently, that amounts to more than 80 pounds, or roughly nine chickens, per year.