Even after the National Association of Realtors (NAR) revised its home-sales data down 14 percent for 2007 through last year, how good is home market information anyway, The Wall Street Journal's Alan Zibel asks.

"The essence of the problem is this: Nobody really knows exactly how many homes are sold in any given year, or month. So the best economists can do is offer their best guess," Zibel wrote Wednesday.

The NAR looks to local listing services for sales information, and listing services are how realtors work. The national group checks against Census data, though that is infrequent.

"Many analysts, however, argue that a better source of data would be from local property records, which are compiled by firms such as CoreLogic Inc. and Lender Processing Services Inc.," Zibel reports.