Milton Friedman: What fascinates me so about economic systems is that the fundamental principles are so simple. You feel as if anybody could learn in two days the basic fundamentals of economics. They’re very simple. The elementary principles of economics are trivial:  People can spend their own money better than they can spend — more carefully than they’ll spend anybody else’s.  Buy low, sell high. Go down — the principles are very simple. And yet, it seems to be so hard for people to understand them. And people so often get them wrong. And the major reason they do — and this is what is really fascinating — is that almost always what’s true for the individual is the opposite of what’s true for everybody put together.

You go down the street and you buy some strawberries. You think you can buy as many strawberries as you want at the price that’s posted. And you’re right. But let’s suppose everybody in the country tried to buy more strawberries. There wouldn’t be any more strawberries. The total quantity of strawberries is fixed. The price would have to go up.  So from the point of view of the individual, the quantity is variable and the price is fixed. For everybody together, the quantity is fixed and the price is variable. And what’s true for strawberries is true for almost everything you can think of. And that’s why, in my opinion, ordinary people are so subject to economic fallacies, because they tend to extrapolate from what’s true for them as an individual to what’s true for everybody. And almost always, that’s a wrong extrapolation.