In the middle of a discussion about the laws of damages, the Babylonian Talmud (Bava Kamma 7b) comments in passing that during that period (roughly 200-500 C.E.), the sale price of land in Israel varied considerably by time of year—by as much as half. This is a startling passage, and for our purposes it helps illuminate some key concepts in economics.

What could be the explanation for such dramatic differences in price? The rabbinic commentator Rashi understands this to mean that between planting and harvest, the expected value of the anticipated harvest was baked into the land’s sale price. By contrast, once the crop had been harvested, the land was reduced to itself, so to speak. So the sale price of the land would rise as we got closer to the harvest, and fall dramatically once the harvest was over.

This explanation has some difficulties. First of all, that would mean that the land itself was only valued at roughly its yield for a single year’s harvest—or even less, if there were multiple harvest seasons over the course of the year. Why would land be so cheap?

The later Tosafists also note that the talmudic passage doesn’t distinguish between farmland and housing. It’s possible that the passage assumed that we would know that it was discussing farmland; but if not, similar price dynamics would be at work in housing as in farmland, even though there is no crop to plant or harvest. So then what would cause the variation? The Tosafists tentatively suggest that demand for housing followed cyclical patterns, rising during the fall and falling at other times of the year. But that is just a way of restating the original question. What drove these patterns? And whatever the cause, why would the price swings be so dramatic?

I have no insight into why housing might exhibit seasonal patterns; but I think I can add a suggestion for why the price variation was so large. If we assume that the “intrinsic” value of the land was not small—and the Talmud makes clear in many places that land ownership was valued and valuable—there must be something at work that changed the expected value of land, meaning the expectation that the land’s owner would be able to benefit from owning the land.

“Expected value” is basically the value of a good, times the chance that you will gain the value. For example, if I say that I will give you a dollar, the expected value of the dollar is $1. But if I give you a dollar only if you win a coin flip, then the expected value of the dollar is only fifty cents. It’s the same dollar; but because you’re less likely to get it, it is worth less to you in advance, while you are still uncertain of the outcome. If Bob wanted to buy from you the chance to do the coin flip, he would only be willing to pay fifty cents, not a dollar. The uncertainty of the asset depresses its price.

And in fact, at the time of the Talmud, land ownership was very insecure. There are many references in the Talmud (for example, Gittin 58b) to people having their land stripped from them by “extortionists,” who apparently took advantage of the weak governmental authority of the occupying power to take people’s lands by force. This would have the effect of depressing land values, because the expected value of the land would be less than if landownership were secure. However, as you got closer to harvest, the likelihood that an extortionist would suddenly take your land before harvest became vanishingly small, increasing the expected value of the land and the harvest, for the moment.

This is related to the argument of Peruvian economist (and sometime politician) Hernando de Soto that informal communities without legal land tenure were poorer as a result (partly because their land or houses could not serve as collateral for secured loans). While that says nothing about whether poor people would actually benefit from getting legal title, instead of whatever informal arrangements they themselves developed in the meantime (in Peru, formalization of title did not lead to significant decreases in poverty, though it was useful in kneecapping the violent insurgency of the Sendero Luminoso), it does highlight the role of certainty and uncertainty in economic value.

So what can worldbuilders get out of this? Most importantly, the insight that changes in likelihood lead to changes in price. Uncertainty causes loss. Certainty is valuable, and people are willing to pay for it. (Which is why the insurance industry exists.) And with some thought, you can use this concept to drive some pretty interesting plot conflicts.

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(This post is part of Politics for Worldbuilders, an occasional series. Many of the previous posts in this series eventually became grist for my handbook for authors and game designers, Beyond Kings and Princesses: Governments for Worldbuilders. The topic of this post belongs in the planned second book in this series, working title Wealth [Commerce?] for Worldbuilders. No idea when it will be finished, but it should be fun!)