Alan Mendelevich's AdDuplex is a mobile ad platform concentrating in Windows Phone. As such, we always get a heavy flow of Windows Phone data from his Twitter account. According to the latest information, the entry level Lumia twins, the Nokia Lumia 520 and the T-Mobile branded Nokia Lumia 521, together make up a whopping 30% of the Windows Phone handsets used around the globe.Perhaps revealing that people would rather buy value, even in the U.S., the Nokia Lumia 520 has replaced the Nokia Lumia 920 as the second most used Windows Phone in the states. And that has led both the Lumia 520 and Lumia 521 to control more than 30% of the Windows Phone market in the U.S.And yes, the sales of the entry level models are taking away from purchases of high-end devices like the Nokia Lumia 1520 . Despite the high-end specs and that dynamite 6 inch screen, the flagship model is only number 16 on the Windows Phone charts, based on the data mined by AdDuplex. The Nokia Lumia 1020 , with its 41MP PureView snapper, is number 11. Both account for less than 3% of Windows Phone usage globally.As for the future of the Nokia Lumia 520/521in the states, the Finnish OEM has just launched the Nokia Lumia 525 with mostly the same specs as the twins, but with double the RAM (1GB). This allows the phone to run the latest apps and games from the Windows Phone Store. So far, Nokia has yet to announce any U.S. launch of the updated model.source: @ailon via WMPoweruser