Everybody knows what drought is, right? It’s when lawns start to brown, creeks dry up, and you get a water conservation notice from the local utility. For the Colorado farmers in Lydia DePillis’s story, drought is a threat to their livelihoods — and getting their counties recognized as drought disaster zones means access to emergency loans and grants.

Drought, in other words, is more than a meteorological phenomenon. It’s political, too.

The U.S. Department of Agriculture makes the determination, which historically has been a matter of judgment as much as it has been a matter of science. In 2012, the rules were streamlined so that counties experiencing eight consecutive weeks of “severe drought,” as determined by the scientists at the U.S. Drought Monitor, are immediately enrolled into the emergency program.

Even the researchers at the U.S. Drought Monitor, though, maintain that their drought maps aren’t “a strictly quantitative product.” In addition to looking at rainfall patterns, soil moisture, and temperatures, they also poll a network of 350 on-the-ground experts who give their own (sometimes conflicting) accounts of local conditions. The scientists call the resulting mix a “state-of-the-art blend of science and subjectivity.”

This is not far off from how the National Bureau of Economic Research determines the start and end dates of a recession. A committee of experts examines the economic data and makes a call. To outsiders, the process can sometimes seem like the committee is looking for its own shadow, and there is no shortage of critics. But this all serves as a reminder that numbers can’t speak for themselves. Someone has to interpret them.