Microsoft sold about 5.8 million Lumia smartphones in a mere two months, a pretty impressive number considering nobody you know actually owns a Windows Phone. Out of all of the Windows-based phones in the wild, one model is far more popular than any other: the Lumia 520, which makes up 31.6 percent of all active Windows phones, according to AdDuplex. Add in the slight variant 521 and you have 36.4 percent of the phone's OS share covered by what is essentially one model.
The 520 is also ancient and doesn't even support 4G. But it is insanely cheap, often going on sale for less than $100 for a fully functioning smartphone.
It's successor, the $114 Nokia Lumia 530, has big shoes to fill. The new phone is not only important for helping Microsoft to capture low-end market share (against the flood of quality low-end Android devices from Motorola and others), but it also brings all of the latest Windows Phone 8.1 features to the masses, most notably Cortana.