Economists don’t wear capes. But in an unconventional new book, Marian Tupy and Gale Pooley take on a villain familiar to fans of the Avengers movies: Thanos. The intergalactic warlord tried to kill half of all living beings because he feared that overpopulation would consume the universe’s finite resources. 

In “Superabundance,” the political economists cite Thanos as an example of the still-influential Malthusian idea that population growth will outpace the world’s ability to feed everyone. As a counterargument, they examine the trend lines of “time prices,” the length of time that a person has to work to earn enough money to buy something. In 1850, a factory worker had to work 2 hours and 50 minutes to buy a pound of sugar. In 2021, the same amount of sugar costs just 35 seconds of work.

“Commodities, but also food and even some services – certainly finished goods – are becoming more abundant every 20 years,” says Mr. Tupy, a senior fellow at the libertarian Cato Institute. “Every 1% increase in population reduces time prices of goods and services by 1%. And that tells you that, on average, every human being produces more than they consume.”

The idea that resources are becoming less scarce with increasing population is counterintuitive. There are a finite number of atoms on Earth, says Mr. Tupy, but ideas are infinite. A population of 8 billion will produce more groundbreaking innovations than the 14 million people who inhabited the world as late as 3000 B.C. There’s one other major difference between modern and ancient times: the spread of human cooperation and the ability to share knowledge. 

The two authors believe such innovation is the key to solving environmental problems, such as reducing trash. In the 1950s, for instance, it took 3 ounces of tin to produce a can of Coca-Cola. Now it’s half an ounce. 

How would Mr. Tupy respond to critics who argue that the perpetual growth of material goods is a poor definition of prosperity?

“The more time we have to spend at work, the less time we have on other things,” says Mr. Tupy. “Having the extra time to do other things is, in our view, a good measure of prosperity.”