Housing prices drop 13 percent -- what does this mean?

The New York Times reports on bad housing news:

The median price of a home plunged 13 percent from October to November, to $181,300 from $208,000 a year ago. That was the lowest price since February 2004.

They mean that house prices have gone down 13 percent in a year, i. e. from November 2007 to November 2008. That's what the National Association of Realtors press release says.

But one sees this pretty often -- the confusion between monthly declines and annual declines. And sometimes a 1% decline in a month might be reported as a "12% per year" decline -- but then the "per year" gets dropped, the statement "prices of X dropped 12% this month" is made, and those who aren't familiar with how people who care about the price of X report their numbers get confused.

Don't get me wrong -- a drop of 13% in a year is still a big deal. But a drop of 13% in a month would be a much bigger deal.