Nokia released the company's Q4 2013 financial report earlier this week, revealing some rather disappointing data. Sales of Lumia Windows Phones were estimated to be lower in Q4 2013, compared to Q3. While Nokia failed to provide hard numbers in the report itself, the company did go on record to confirm the number of sales at 8.2 million units (compared to 8.8 in Q3). Then again, even the juggernaut Samsung Mobile had a rough time this quarter, meaning this isn't a Nokia anomaly. Today, AdDuplex, one of the largest ad service providers for Windows Phone apps, has published a blog post attempting to analyse how the platform performed through the holiday season, compared to previous quarters. Best VPN providers 2020: Learn about ExpressVPN, NordVPN & more

Microsoft's Joe Belfiore also took to Windows Phone's defence with the following tweet:

That statement was previously conveyed to us by Microsoft in our interview with Windows Phone Director, Greg Sullivan, this month at CES. Calculations in the AdDuplex blog post aren't entirely based on hard data, but it's a good look at how the platform has progressed through 2013. Throwing data from the last 12 months together (comparing Windows Phone 7 against Windows Phone 8) and publishing a chart, you get the following:

What this chart conveys is how Windows Phone 8 advanced from just 19 percent of all Windows Phones (included in the samples) to over 78 percent. AdDuplex refrained from calculating Windows Phone sales numbers using accumulated data in monthly reports, but to help shed some light on the situation, a few assumptions have been thrown into the mix. Reading on, you're to assume that sales of Windows Phone 7 hardware weren't substantial during 2013 and the number of devices in use decreased by 2 percent per-month. "We need to figure out how many Windows Phone 7 devices were in use by January 2013. This post on The Verge suggests that Nokia sold 13.3 million Lumias in 2012 and another million in 2011. By the end of 2012 Nokia had ~75% share of the Windows Phones in use. So that makes around 19 million WPs in total. A few of the phones sold were already WP8 and some were already out of use (broken/returned/etc.). So let’s say 12 million WP7 were in use by the end of 2013. Another pretty baseless assumption, but again, not essential for the issue in question." Basing the below chart on both data and the established assumptions above, AdDuplex ended up with the results of the total number of Windows Phone 8 devices in active use: