Remember back when all your friends were buying apartment or houses and kidding themselves that it was an "investment?"

During the boom, it wasn't infrequent for people to buy places smaller than the apartment they had been renting. Worse, they often wound up paying more in mortgage payments than they had in rent. Why pay more for less? The answer always was something about how owning your a place of your own was an "investment."

Well, for many Americans it turned out to be a pretty damned lousy investment. Now Karen Pence, who runs the household and real estate finance research group, has been explaining to the meeting of the American Economic Association that this wasn't just a fluke of the housing boom and bust. Buying a home is usually a lousy investment.

Here are her five reasons:

1. It is an indivisible asset. If you own stocks and bonds and suddenly need a little cash, you can sell some of your stocks or bonds but not all. With a home, on the other hand, “you can’t just slice off your bathroom and sell it on the market.”

2. It is undiversified. You can buy stocks or bonds in industries or countries all over the world. A home is a bet on one single neighborhood.

3. Transaction costs are very high when you buy or sell a home because of real estate agent fees, mortgage fees and moving costs.

4. It is asymmetrically liquid, meaning it’s easy to get money out when home prices are going up. (You just take out a bigger mortgage.) But it’s hard to take money out when prices are going down because refinancing becomes more difficult. Put another way, the leverage that you have in your house with a large mortgage means your investment does well in good times but could be lousy in bad times.

5. It is highly correlated to the job market, meaning that home prices in a neighborhood tend to rise when the job market is improving in the area and fall when the job market is worsening. This means that your main financial asset provides the smallest cushion to you when you might need it most.

That doesn't mean you should never buy. Under the right circumstances, buying a home can make perfect sense. But don't count on it as an "investment," especially if you might need to access the money you locked up in the house at any particular point in time. On the short term, that money might not be readily available when you need it. And in the long term, for instance upon retirement, you might also find a bear market for homes.