Interesting read:
insight.kellogg.northwestern.edu

The Hedge Fund in Your Pantry
Many households utilize excess cash to support shopping habits that generate high financial returns.

If you had an extra $500 in your checking account, what would be a rational thing to do with it? All things being equal, many experts would recommend investing it in the stock market, where the average annual return of 10 percent handily beats the pitiful interest rates offered by most retail savings accounts. But few households actually do this—especially lower-income ones. Are they acting irrationally?
Hardly, says Scott Baker, an associate professor of finance at the Kellogg School. New research from Baker and his collaborators Stephanie Johnson and Lorenz Kueng (of Rice University and the Swiss Finance Institute, respectively) shows that many households “invest” surplus cash in an inventory of common household consumables—everything from canned goods and breakfast cereal to boxes of tissue and rolls of toilet paper.