Distimo has issued a study called Windows Phone 7 Marketplace: One Year Later that examines Microsoft's latest mobile apps store and how its evolved over the past twelve months. This study is interesting in its own right, and it has me wondering about mobile apps and how Windows Phone really fares against other platforms.

As you may recall, Microsoft launched Windows Phone Marketplace in October 2010, just a few weeks before the first Windows Phone handsets became available to consumers. Not surprisingly, a lot has changed since then.

"This month's publication covers the first year of the Windows Phone 7 Marketplace," the company told me. "The Windows Phone 7  was introduced in 17 countries with an additional 18 countries added later. The latest Distimo monthly report tells the story of an emerging application store and the behavior of developers in the store. This report includes all 35 countries in the Windows Phone 7 Marketplace is currently available."

According to Distimo, the major findings are:

The Windows Phone 7 Marketplace has the highest download volume in the United States with 101,000 free downloads and 20,000 paid downloads per day. Here, the download volume of the Windows Phone 7 Marketplace is 39 times smaller relative to the download volume in the Apple App Store for iPhone.

Paid applications in the Windows Phone 7 Marketplace have grown continuously with almost 1300 new paid applications every month. Free applications have increased on average by 1650 new free applications month-over-month.

The number of publishers has consistently grown since the launch of the Windows Phone 7 Marketplace, with 700 new publishers per month.

Nearly 50 percent of all applications are available in the 17 countries in which the Windows Phone 7 Marketplace was originally accessible. One-third of all applications are available in all 35 countries.

Developers find it easier to distribute paid content globally instead of free content. Free content is more localized in the Windows Phone 7 Marketplace.

The most popular category in the Windows Phone 7 Marketplace is Games. Other popular categories are Tools & Productivity, Entertainment and Travel & Navigation.

Looking at the actual report, a few other details stand out. For example, Distimo claims that the Window Phone Marketplace is now the "fifth-largest OS application store," behind Apple's App Store, Google's Android Market, the Nokia Ovi Store, and Blackberry App World. It's worth reading fully, as there are also some useful and illustrative graphs and tables.

But I'm a bit more interested in the study's top 10 apps lists for various mobile platforms. Looking at these lists, it's possible to figure out which and how many of the top apps on other platforms are available on Windows Phone too. (Obviously, this isn't definitive. These aren't the top 10 apps of all time but are rather a slice in time look at each respective store, in this case for October 2011.)

Let's use the Apple App Store as an obvious example.

Of the top 10 free apps available to iOS/iPhone users, only 2 are available on Windows Phone too: Adobe Reader (#2) and Facebook (#3). But 8 are not, including Skype (#1), Six Towers (#4), My Country (#5), Pioneer Lands (#6), Talking Tom and Ben News (#7), iBooks (#8), Card Ace: Casino (#9), and My Sketch (#10).

Now, some of those missing apps have decent alternatives; Amazon's Kindle app is a better eBook solution than iBooks, for example. But you get the idea. Many of these apps will never be ported to Windows Phone, or will be ported months from now.

For the heck of it, I decided to look at the top 10 list of apps on Windows Phone Marketplace today and see how many of them were available, conversely, on iOS/iPhone. This is even more of a slice in time since it literally changes continuously. But this is what I found:

Of the top 10 apps in the Windows Phone Marketplace, 8 were available on iOS/iPhone: Angry Birds (#1), Burn the Rope (#3), Let's Golf 2 (#5), Jet Car Stunts (#6), Fruit Ninja (#7), Sonic the Hedgehog (#8), Need for Speed Undercover (#9), and Gravity Guy (#10). Only 2 were not: Kinectimals (#2), Fusion and Sentinal (#4).

But here's the thing. Of those 8 games that are available on both platforms, many (Angry Birds, Let's Golf 2, Need for Speed, etc.) were older games with which the developer has released one or more sequels. And those sequels are available on iOS/iPhone ... but not Windows Phone.

Let's look at Angry Birds. Rovio has released numerous versions of this game, including the original, Angry Birds Seasons, and Angry Birds Rio, and it has continuously updated some of them with new levels over time. On Windows Phone, we have only the original game. That game first shipped on the iPhone in December 2009.

So this is the divide that Windows Phone still needs to conquer, I think. Not just a certain quantity of apps, but rather a certain selection of apps. I know that there are people at Microsoft who do nothing but work on this. But there's still much to do.