Retail sales are a pretty good proxy for consumer spending, so to me, any nationwide drop in retail sales is a warning flag about our consumption-based economy.

The Wall Street crowd was pretty surprised when the Commerce Department reported that Americans pulled back spending in July. Retail sales numbers for July came in at a disappointing 0 percent, well below the 0.4 percent Wall Street had expected.

Even that 0 percent number is misleading. After backing out auto sales, retail sales actually declined by 0.3 percent in July.

Remember, this consumer-spending slowdown is happening against a backdrop of much lower gas prices and (supposedly) an improving job market.

My guess is that American consumers are simply running into a brick wall of too much debt: