For those who believe that economics has never done anything useful or benefits the common man, here's a small counterclaim.

The widespread adoption of index funds was absolutely an outgrowth of academic financial economics. In particular the efficient market hypothesis and CAPM theories, as well as empirical research studying the (lack of) performance of active investment managers.

In the US alone, index funds now make up more than $3 trillion of assets. That's saving investors more than $30 billion in wasteful fees every single year. (Which doesn't even account for the downward pressure on fees for active funds.) Moreover this revolution has benefited ordinary and small investors the most.