Retail Sales? They're Up. Or Down. Or Flat.

Government statistics on November retail sales don't come out until tomorrow, but Mastercard Advisors today released its own November retail sales data today, based on spending data from MasterCard cards coupled with estimates for all other payment forms, including cash and check.

SpendingPulse data reveals that consumers spent 5.5 percent less in the month of November they did at the same time last year.

Don't like that number? Okay, then consumers spent the same amount they did in November 2007.

It all depends on which figures you look at.

Once you take into account seasonal adjustment - statistical voodoo commonly used to even out intra-year data inconsistencies- the number shrinks to a 3.8 percent spending decrease in November, according to Mastercard Advisors.

That figure was still the largest one-month drop since they started releasing SpendingPulse data in 2003, surpassing the prior record fall of 2.4 percent set in September.

The above figures already exclude auto sales, but if you exclude gasoline sales as well, November retail sales were down 2.5 percent from the year-earlier period.

Gas prices fell by about 25 percent this past month, and sales of gasoline make up 10 percent to 15 percent of consumer spending, meaning that that volatility can have a appreciable impact in monthly sales.

Still, retail sales excluding gasoline fell by a mere 0.3 percent in October, so by that measure things still look significantly worse in November.

But don't forget about the calendar shift! There were five fewer shopping days this year between Thanksgiving and the end of November than there were last year. When MasterCard Advisors tries to account for that difference, it estimates that sales were either flat or down 0.5 percent compared with last November.

Anyway, this is all by way of saying that it's wise to take any retail sales data not published by the Commerce Department with a grain of salt; also, it's safer to pay attention to month-to-month or year-to-year trends than to absolute numbers.

The great many sources of data out there and the numerous variations in what they take into account makes it easy to start comparing apples to oranges.

by Liz Gunnison