Amazon: The Scrooge of Holiday-Sales Data

I spent five times as much on Christmas presents this year as last year.

That is, I spent $500 in one frenzied day of shopping. Last year, I spent $100 a day over 10 days of shopping.

OK, I made those figures up, but you can see the problem with such selective statistics. I can pretend my spending increased fivefold when in fact it was really cut in half. And yet that’s how Amazon slices and dices its closely watched holiday sales numbers.

Amazon (s amzn) says customers ordered “over 6.3 million items ordered worldwide on the peak day, Dec. 15” (or a “record-breaking” 73 items per second!). That raises more questions than it answers. Why focus on just one day? Do “items” include individual MP3 files? Why not just tally the total dollar value of all the goods it sold? We could be buying more items but spending so little on each that Amazon’s total sales decline.

So when Amazon released its annual “best-year-ever” PR release after Christmas, the celebration was even briefer than a Festivus party at the Costanzas. Amazon’s stock rose 4.6 percent early Friday to $53.79, but closed pretty much unchanged at $51.78.

Observers noted that not only was the shopping season shorter this year by five days, but the growth rate of Amazon’s “peak day” slowed to 17 percent this year from 35 percent in 2007. Others chided Amazon for being tightfisted with numbers during a holiday season in need of good news. Paul Kedrosky went gloomier, suggesting Amazon could itself fall victim to weakening sales.

Instead, Amazon offers slightly cute and completely useless factoids, like how far all the Coldplay CDs that Amazon sold would stretch if laid side by side (an exercise useful only if you bring in a steamroller).

Amazon’s technical expertise is good enough that they are capable of offering a window into the mind of the American consumer — which has changed drastically in the past three months. We saw a taste of this further down into the press release, where Amazon listed the top-selling products this season in each major category.

Among gadgets, consumers weren’t going for the cheapest-priced items, preferring quality at good value. Apple’s iPod Touch (s aapl) was a bestseller, as was an Acer netbook retailing for $370 and a 52-inch Samsung HDTV at $1,800. Nintendo’s Wii, unsurprisingly, dominated video game sales.

Culturally, Amazon’s sales suggest consumers fixated on dark tones. The gothic “Twilight,” with its tale of forbidden and protective love, topped books and its movie soundtrack also sold well. Apocalyptic themes in “Wall-E” and “The Dark Knight” resonated in DVD sales. The darkness fetish even extended into the toys category, where Eyeclops night vision stealth goggles were the top seller.

Insight into how long this sour mood might last. Too bad that Amazon, so good at collecting this kind of data, is so bad at sharing it.