Another month, another revealing peek at Windows Phone device usage statistics, courtesy of AdDuplex. This month, we see the continued domination of low-end devices, plus the Lumia 630 hits the charts for the first time.

As you may remember, AdDuplex bills itself as the largest cross-promotion network for Windows Phone and Windows 8 apps, empowering developers and publishers to promote their apps for free by helping each other. And each month it provides a tantalizing glimpse at which Windows Phone (and Windows) devices people are actually using.

Some trends from this month's report include:

Lumia 520 is still on top, of course. Last month, AdDuplex noted that the Lumia 520's year-long growth had finally come to a stop. And sure enough, this month, 520 usage actually declined a bit (0.6 percent). But it still controls almost 34 percent of all Windows Phone usage worldwide, and if you add in the basically identical Lumia 521, which is actually still growing for some reason, it hits over 40 percent.

Lumia 625 is number two. This low-end, big screen device debuted a year ago and has been slowly making its way up the charts. This month, it's number two overall, with 6.7 percent usage, ahead of the aging Lumia 920 (6.2 percent).

Lumia 630 hits the charts, sort of. New Lumias often debut low on the usage charts, and some of the high-end units—like the Lumia 1020 and 1520—never make it anywhere near the top 10. But the Lumia 930, which can think of as the international/GSM version of the Lumia Icon entered the charts this month at #30. Which doesn't sound good until you realize that's already a higher usage point than the Icon.

Low-end rules. We've known since last year that low-end Windows Phones handily outsell mid-level and high-end devices, but this month AdDuplex neatly formalized this concept with a more visual view of how these phone types break down. You can see here that low-end Windows Phone 8 handsets represent fully 53 percent of all Windows Phone handsets in use, with other (non-high-end) devices, including some WP7 handsets, making up almost 33 percent. Put another way, only 14.2 percent of all Windows Phone handsets in use are high-end (and/or phablet) devices.

Nokia still dominates. Nokia devices accounted for almost 94 percent of all Windows Phone handsets in use in May, compared to 4.3 percent for HTC, 1.2 percent for Samsung and 0.8 percent for Huawei.

Windows Phone 8.1 surges. While only 5.2 percent of all Windows Phone handsets in use are running Windows Phone 8.1, it's important to remember that this version of the OS is only technically available to developers through a Preview program. That's pretty amazing, then. Windows Phone 8.0 is on 77 percent of all Windows Phone handsets in use, with WP7 taking up 17.8 percent.

Interesting stuff, as always.