Mobile Windows market share stabilizes, but it could be too late to save the patient

Microsoft's share of U.S. smartphone market has stopped falling -- too bad Microsoft won't say which of its devices are selling

For the past year, Microsoft's share of the U.S. smartphone market has been falling like a rock, but in the past three months, it's stabilized. That's a notable achievement, in no small part because the market itself has grown so much, rising 2 to 3 percent per month.

To understand comScore's numbers, you have to take into consideration just what they're measuring. Every month, comScore publishes three-month moving averages of smartphone market share. It surveys 30,000 smartphone owners in the United States, age 13 and over, and asks them which phone they use.

As you can see, the lagging-three-month averages for RIM and Symbian (and before that, Palm) have headed south. No surprise. The percentage of people who claimed to use an Apple phone has gone up slightly, from 24.2 percent in August of last year to 27.3 percent in August of this year. Google's gone through the roof, from 19.6 percent to 43.7 percent in August this year.

The surprising number? Microsoft's three-month-average market share plummeted from 10.8 percent in August last year to 5.8 percent in May of this year -- painfully close to falling by half -- but since May, the losses have stabilized, with Windows running at 5.7 to 5.8 percent of the market.

Though comScore doesn't publish worldwide smartphone numbers, in the five leading European markets (France, Germany, Italy, Spain, and the United Kingdom), Microsoft dropped from 11.5 percent of the market in July 2010 to 6.7 percent of the market in July 2011.

Don't jump out of your seat and start chanting, "Developers, developers, developers," just yet. The comScore numbers tell an important tale -- how many people report owning a Windows-powered phone -- but there are two other numbers that warrant attention.

Online media measuring company Net Applications measures how often mobile devices are used to access one of its 40,000 tracked sites. I've talked about their NetMarketShare reports many times, most recently in describing how Internet Explorer is rapidly falling to 50 percent of desktop browser use and how the "iPad effect" has greatly increased mobile browser usage numbers.

The sample base for comScore and Net Applications varies significantly. For starters, comScore asks U.S. smartphone owners which phone they own. Net Applications looks at all websites, all over the world, and reports on which operating systems are being used to power the browsers.