Almost all science fiction and fantasy stories are, at their core, about the economics of scarcity and abundance.

That's the idea behind "Economics of Thrones and Starships," the latest episode in the podcast series "Imaginary Worlds." The episode explores the impact of economics on science fiction and fantasy universes. The first segment, in which host Eric Molinsky and Sarah Skwire, a writer and fellow at the libertarian Liberty Fund think tank, discuss scarcity and abundance, is especially revealing.

In economics, scarcity refers to the idea that world's limited resources can never meet every human want. Abundance refers to situations where supplies are so high that most (if not all) human wants and needs are met. And, according the Skwire, nearly all fantasy and science fiction can be understood in those terms.

"Economics is about the choices we make as humans, the things we want as humans, and what we're willing to trade for those things," she says. Authors do the same thing.

Economists like to perform thought experiments where they tweak the real conditions that prevail in our world, and replace them with imaginary scenarios. When authors do that, it's called science fiction or fantasy.

Skwire tells Molinsky that from stories like "Star Trek" and books from the sci-fi's "golden age" in the '30s and '40s answer the question What would people do with their time and energy if scarcity ended? In the "Star Trek" universe, replicators and holo-decks can feed the world and offer endless entertainment. That glut of resources creates the necessary conditions for the sort of bold, resource-heavy exploration and adventure on which the characters embark.

More recent stories, she says, tend to reverse the dynamic, imagining situations of extreme scarcity. In "The Martian," for example, astronaut Mark Watney finds himself alone on Mars with little but a survival pod, the red planet's lifeless soil, some potatoes, and the detritus of past missions. But he prevails. Post-apocalyptic stories like "Station Eleven," "The Walking Dead," "The Stand," and "The Road" envision similar scenarios.

Skwire tells Molinsky that which side of the scarcity/abundance divide authors fall on can tell you a lot about the time and place in which they're writing.

"In times when resources are scarce, people fantasize about worlds of great abundance. And in times when we have a lot of stuff like we do now, we fantasize about scarcity and about pioneering new territories and about how to get along on less and less stuff."

We've named "Imaginary Worlds" one of the 45 best podcasts in the world. You can listen to the full episode here: