Microsoft has announced it has sold over 200 million licences for its Windows 8 operating system in the first update the company has made regarding sales since May 2013.

Speaking at a technology conference in San Francisco on Thursday, Microsoft’s vice president of marketing Temi Reller referred to the figure as “pretty stunning”. The figure of 200 million sales pales, however, in comparison to the standard set by Windows 7, which shifted 240 million units within a year of release. Windows 8 has now been on the market for 15 months, making the figure of 200 million disappointing by comparison.

In fact, Reller’s comments suggest that sales of the operating system have slowed over the past nine months: Reller’s first announcement in May 2013 was that 100 million licenses had been sold in the first six months since Windows 8’s release. Selling the same number in the following nine months confirms many analysts’ suspicions that Windows 8 is struggling. It should be noted though that many of the 100 million licenses sold in the first six months would have sold to original equipment manufacturers (OEMs) for future use in Windows 8 machines not yet built.

There is an inevitable discrepancy between the number of licences sold and the number of devices currently being ran with Windows 8. Estimates of the number of licenses actually in use vary, but it is likely that less than half of licenses sold so far are actually in current use.

Windows 8 has been widely criticised by both industry experts and consumers due to its unwelcome divergence from the familiar Windows interface of earlier operating systems. The free update Windows 8.1, released in October 2013, has gone some way to win over critics, though many users are still reluctant to upgrade to a new Windows 8 PC.

Windows 8’s struggles are just part of a general trend in the PC market, which has seen sales slow as smartphones and tablets grow in popularity. Within this wider context, Windows 8’s performance appears fairly robust. Sales of Windows 8 machines may well pick up in the coming months in anticipation of Microsoft’s end of security support for the XP operating system.