Existing home sales
Source: National Association of Realtors

After a week of mixed housing market indicators, we finally have one that shows some firm good news. Sales of existing homes rose in July, for the fourth consecutive month, according to the National Association of Realtors. They're up 7.2 percent from last month, and 5 percent from year ago. It's the largest gain since record-keeping began in 1999.

Overall, July existing home sales hit a seasonally-adjusted annualized rate of 5.24 million, far exceeding expert predictions of 5 million. Experts attributed the increase to the housing stimulus tax credit, and the best housing affordability in two decades. According to the report, the median price of existing homes fell 15 percent.

If the building boom and housing bust lead to too many empty houses, an increase in home sales is a very good sign — it means that some of those houses are starting to be filled, which could encourage home builders to start building again. Still, at the current pace, it would take 9.4 months to sell every previously-owned home on the market. In a stable market, it should only take seven months.