It’s blood.
America is one of the only developed countries in the world that pays people to donate blood, much of it sold abroad (70% of the world’s plasma is of US origin), and as commercial blood donations have soared, blood now accounts for 2% of the country’s exports — more than corn or soya.
There’s more growth ahead for blood products, expected to “grow radiantly” according to an analyst who was cheering 13% growth between 2016-17.
I had a hard time believing that, so I checked the source, and sure enough, 2.3% of US exports are of human or animal blood and vaccines, and it’s more than the value of our corn and soybean exports. To put it in perspective, though, our exports of refined petroleum are worth more than twice that.
So, I guess, there’s a market for American blood and oil.
If inequality continues as it has, perhaps there’ll someday a market for other human biological products. Pig meat products are only .36% of our exports, we could expand that by adding long pig.
We could also hope for a big boom in the vampire population.