Gartner, an anlayst firm, in its latest report on global smartphone sales estimates that Windows Phone sold 7.41 million devices in the second quarter of the year for a unit market share of 3.3%. Those figures are up year-on-year from 4.039 million and 2.6% respectively. Gartner's number for total smartphone sales in Q2 2013 was 225.326 million units.

In contrast to most research firms Gartner estimates unit sales to end users, rather than unit shipment volumes, which, together with varying metholodology and sampling technique, helps explains why Gartner's numbers are slightly different to IDC and Strategy Analytics.

Gartner's number for Windows Phones sales in Q2 2013 is a little lower then expected, which could potentially be evidence that there has been an increase in inventory levels of Windows Phone devices held by retailers and operators. However, this should be set against the fact that Nokia, in its Q2 finanical results, reported shipments of 7.4 million Lumia devices, but, at the same time, noted that inventory levels for Q2 2013 were broadly similar to the previous quarter. 

According to Gartner's estimates Q2 2013 was the first time that Windows Phone over took BlackBerry for the number three spot of smartphones unit sales by platform. Anshul Gupta, principal research analyst at Gartner noted that Microsoft needed to continue to focus on developer relations:

“While Microsoft has managed to increase share and volume in the quarter, Microsoft should continue to focus on growing interest from app developers to help grow its appeal among users.” 

Gupta also commented on Nokia's Lumia portfolio in the Gartner press release:

 “With the recent announcement of the Lumia 1020, Nokia has built a wide portfolio of devices at multiple price points, which should boost Lumia sales in the second half of 2013. However, Nokia is facing tough competition from Android devices, especially from regional and Chinese manufacturers which are more aggressive in terms of price points.”