If you track home sales in neighborhoods near you, you probably have some idea why average and median price changes aren't always helpful measures. Even streets with apparently cookie-cutter houses have variations -- this one is updated, that one is pure '70s. In communities where the homes range from two-bedroom rancher to 4,000-square-foot manor, what sells one year might have no relation to sales the next.

That's why home buyers, sellers and agents (and state officials sorting through property tax appeals) focus on "comps." What's actually comparable?

If you want to know how Baltimore City or Carroll County or any individual jurisdiction fared in any particular month, you're basically stuck with average and median. That's what Metropolitan Regional Information Systems reports.

But there are other figures you can look at, if you don't mind waiting and/or taking the bigger perspective of the metro area overall.

The much-watched Case-Shiller index doesn't include Baltimore (Washington is as close as it gets), but the Office of Federal Housing Enterprise Oversight tracks the area. OFHEO measures repeat transactions -- changes in price to the same home over time. According to its number-crunching, prices dropped almost 6 percent in the Baltimore metro area during the last three months of 2008, compared with a year earlier.

The downside: a time lag, as you can see. Also, the figures include only single-family homes bought or refinanced with "conforming" loans, which means it's not capturing the universe of subprime and jumbo.

Real estate information company First American CoreLogic also tracks "increases and decreases in sales prices for the same homes over time," but it includes nonconforming mortgages. By its reckoning, prices in the Baltimore metro area dropped 8 percent in January vs. a year earlier.

That's precisely the same as the median price drop according to MRIS, as it happens. So sometimes the different measures do agree.