Now Playing: 3-6-13 Marketplace

Managers might send out dozens of “great job” emails each day -- but does it help motivate employees? Freakonomics finds out. Adriene Hill takes a look at why the Dow Jones Industrial Average still commands so much attention. The FAA has released a list of 173 airports that could have their control towers closed next month because of budget cuts. Freight railroad operator BNSF announced it's switching from diesel fuel to natural gas. Families are hiring financial advisers to help them squeeze out every possible penny for college. And author Jonah Berger talks about why things become trendy.