For decades, people have wondered what will happen to the economy when the baby boomers retire. 

Will stock prices fall as boomers liquidate their 401(k)s?

Will the economy stall as aging boomers spend less money? 

Will Social Security run dry? 

They're all good questions. Retiring boomers will have a big impact on the economy. 

But there's another demographic shift that doesn't get nearly enough attention. 

In this video, Motley Fool analyst Morgan Housel sits down with Matt Trogdon to discuss what it is, and how it'll impact the economy in the coming decades.