How Do 400 Million Windows 7 Licenses Compare Against Windows XP and Vista History?

Steve Ballmer proudly announced that Microsoft has sold 400 million Windows 7 licenses. It's a big number by any measure, but how does it compare to Windows Vista and Windows XP?

It has become a tradition for me that I am looking a bit closer into Microsoft's operating system license shipments every time Microsoft announces a new number with the subtle remark that a certain Windows is the fastest selling operating system ever. I don't know about you, but I never heard Microsoft ever announcing that any of its OSes was not the fastest selling OS in Windows history. Even Vista was, apparently, but we know that Vista wasn't exactly a success which tells us that a big number does not mean necessarily that a particular OS is a big success.

So, do 400 million Windows 7 licenses mean that Windows 7 is a big hit? Let's see.

We need to break this number down and put it in perspective to actual PC sales. Windows 7 launched on October 22, 2009 and has sold, on average, about 20 million licenses per month since then (give or take a few hundred thousand per month to even out the pre-sales event preceding the OS launch in 2009). During those 20 months, the global PC industry sold about 591 million PCs, which means that Microsoft shipped about 68 Windows licenses for every 100 PCs sold (let's forget the upgrades for a moment and take this number as a way to compare sales).

What is particularly stunning about the 20 million-per-month number is the fact that it is very consistent and there seems to almost clockwork in play to achieve those 20 million units. 100 million Windows 7 licenses were sold after 6 months, 150 million after 8 months, 240 million after 12 months and 300 million after 15 months. It is almost spooky. Windows 7 sales may be declining just a tad from the 8 month mark, but it's not significant.

Windows Vista, in comparison, sold 128 million licenses in 9 months, or 12 months, if we include the 3-month Express Upgrade cycle that enabled Microsoft to make the 2006/2007 holiday season (Vista was officially released to retail in January 2007, but was available through a coupon beginning in October 2006). So, a fair comparison would be that Vista sold just over 10 million units per month in the first year. Microsoft then announced 180 million units in August 2008 or 19/22 months after launch, which dropped the average to about 8 million units per month: interestingly enough, that means that Windows 7 has outsold Vista already as Windows Vista sold 384 million licenses in a best case scenario (48 months * 8 million units) until it was discontinued in October of last year.

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