Windows 7's marketshare continues to grow at a steady pace at the expense of its two older siblings, Windows Vista and XP, according to the data from StatCounter. In terms of global usage, Windows XP is at 46.44%, Windows Vista at 12.5%, and Windows 7 at 32.64%. Good news for everyone, right? Well, if these adoption numbers aren't convincing enough, perhaps this might convince you (or your technologically challenged peers) - Windows 7 has the lowest infection rates per quarter amongst Microsoft's currently supported operating systems.

The above graph, which was extracted from Microsoft's Security Intelligence Report, shows Windows 7's average infection rates per each quarter in 2010 as 0.38% for 32-bit versions and 0.25% for 64-bit versions. This is about half of Windows Vista SP2's quarterly infection rates and less than a fifth of Windows XP SP3's quarterly infection rates. The tests were conducted on a thousand computers per operating system.

The observations drawn from this chart are made clear in the report:

As in previous periods, infection rates for more recently released operating systems and service packs are consistently lower than earlier ones, for both client and server platforms. Windows 7 and Windows Server® 2008 R2, the most recently released Windows client and server versions, respectively, have the lowest infection rates on the chart.

The lower infection rates from the 64-bit versions was perhaps proof Kernel Patch Protection built into 64-bit versions of Windows Vista and 7 worked, as they noted:

One reason may be that 64-bit versions of Windows still appeal to a more technically savvy audience than their 32-bit counterparts, despite increasing sales of 64-bit Windows versions among the general computing population. Kernel Patch Protection (KPP), a feature of 64-bit versions of Windows that protects the kernel from unauthorized modification, may also contribute to the discrepancy by preventing certain types of malware from operating.

Still a skeptic? Could the lower infection rate be simply due to Windows 7's infancy in the market? This theory would hold if Windows 7's infection rates went up as its marketshare increased, but as this next chart shows, not only did Windows 7's infection rate remain below a quarterly infection rate of 0.4%, there is no clear increase or decrease in infection rates:

The full Security Intelligence Report for 2010 may be viewed here.

Thanks Ci7 for the tip on the forums!