The economic situation we find ourselves in today is a little bit like the example above. Everyone knows that it's a bad thing when factories sit gathering dust and potential workers sit idle on their couches. But the best "experts" that we have -- academic economists -- are in generally ill repute. Surveys have shown that the public has very little confidence in their predictions. They argue bitterly on op-ed pages and can't seem to agree on the most basic issues. And of course, the recent high-profile debunking of the "90 percent debt-to-GDP danger zone" -- a talking point created by the famous economist duo of Carmen Reinhart and Kenneth Rogoff, and used by many Republican supporters of austerity -- did nothing to help economists' reputations.

So are we making a mistake putting our faith in economics? Are economists themselves just charlatans, to be scorned as medieval cranks? Or for all their flaws, are they really the best experts we have? I don't have a definitive answer, just like there is no good answer to the problem of the Royal Physician. But having gone through an economics PhD, I do know a few things that I think the public should realize about the field.

To start, we need to talk briefly about what it is economic theorists do. Essentially, they make models, which are mathematical tools that are supposed to describe how the economy functions. The problem is that economists haven't really built a model of the whole economy that works. A lot of smart people have spent a lot of time creating tools with names like "dynamic stochastic general equilibrium." But as of this moment, those models can't really forecast the economy like our meteorologists can forecast the weather. Furthermore, they contain a lot of obviously wrong assumptions. To give just one example, many of the models stipulate that companies are only allowed to change their prices at random times! Crazy, right? Economists include things like that to make the models easier to use, and they hope that those zany assumptions are actually decent approximations to the way the world really works. But even with these kludges in place, none of the existing models can do much to predict the economy.

Theory isn't the only problem. Economists don't really have good enough data to understand how the economy works, either. With chemistry or biology, you can put things in a lab and test them out with controlled experiments. With microeconomics -- the study of specific markets -- you can do something similar; for example, the auctions that Google uses to sell online ads were developed by microeconomists. But with macroeconomics -- the study of the economy as a whole -- you can't put countries and entire economies in a lab; all you can do is sit there and watch history go by, and try to deduce some patterns. But often enough, those patterns vanish just as soon as you think you've found one.