Shares of businesses return 7% a year over long time periods. I'm subtracting for inflation, gradual price  increases for everything from a can of beer to an ear exam. (After-inflation or "real" returns are the only ones that matter. The point of increasing wealth is to increase buying power, not numbers on an account statement.) Shares have been remarkably consistent over the past two centuries in their 7% real returns.

In Jeremy Siegel's book, "Stocks for the Long Term," he finds that real returns averaged 7.0% over nearly seven decades ending 1870, then 6.6% through 1925 and then 6.9% through 2004.

The average real return for houses over long time periods might surprise you. It's zero.

Shares return 7% a year after inflation because that's how fast companies tend to increase their profits.

Houses have their own version of profits: rents. Tenant-occupied houses generate actual rents while owner-occupied houses generate ones that are implied but no less real: the rents their owners don't have to pay each year. House prices and rents have been closely linked throughout history, with both increasing at the rate of inflation, or about 3%1 a year since 1900. A house, after all, is an ordinary good.

It can't think up ways to drive profits like a company's managers can. Absent artificial boosts to demand, house prices will increase at the rate of inflation over long time periods for a real return of zero.