If you’ve ever been on an overbooked flight, you know the drill: The airline offers vouchers good for future air travel, and usually enough people are willing to trade a little inconvenience today for a free flight later.  What you might not know is that it didn’t always work that way. In the 1960s and 1970s, airlines simply bumped passengers with no compensation, creating a public-relations nightmare. As a result, carriers were very cautious about overbooking, even though they knew from experience that most flights would have a couple of no-shows.

James Heins, a retired University of Illinois economist, calculates that the bumping bonus has been a  $100 billion innovation for the U.S. economy. Airlines make more money by filling their planes closer to capacity, and consumers benefit from lower fares. Now, 30 years after the system changed, Heins is campaigning to gain some recognition for an ex-colleague who came up with the idea.

The late economist Julian Simon was at the U of I when he suggested paying people who agreed to be bumped. Simon finally sold the idea to Alfred Kahn, chairman of the old Civil Aeronautics Board, in 1979.

Like many innovations, we now take the bumping bonus for granted. We shouldn’t, Heins says:

People know about the system, but they don’t know where it came from. I think they should. There are a lot of important research breakthroughs on campuses, but few generate $100 billion in savings to the American economy.