Prospect theory is a descriptive utility concept. Though the wikipedia page makes it seem complex, the idea is essentially that people treat gains and losses differently, reacting more sensitively to losses than to gains. Okay, sure, that seems pretty straightforward. But what makes the idea subtle is that it induces a path dependence that runs counter to traditional notions of utility: two people in the same state can have wildly different utilities just based on the path they took to get there.

What’s interesting is the way that opinions about weather seem to validate this kind of path dependence. Unlike utility, which is essentially a fictional conceit, weather is externally verifiable and (to a large extent totally) objective.

The best illustration of prospect theory in weather is June Gloom, a phenomenon which describes increased early summer cloudiness in (southern) California. June Gloom is real: looking at San Diego’s weather, you can see the dip where the city is about 10% cloudier in May and June. But not only is Pittsburgh cloudier than San Diego in June (58% to 55%), Pittsburgh’s sunniest month is cloudier than every single month in San Diego. But of course there’s no wikipedia page for “Perpetual Pittsburgh Gloom”.

Prospect theory implies a heightened sensitivity to the downside; put another way, the best way to make a bad outcome seem better is to compare it to something even worse. Check out this wonderful line from Buffalo’s wikipedia page:

Buffalo has a reputation for snowy winters, but it is rarely the snowiest city in New York State.

See? It’s not that bad.