It’s taking longer than Google would like for Chromebook sales to shift into second gear. How slow have sales been? After two years on the market, Chromebooks still don’t represent a big enough percentage of the computer market to warrant a spot on NetMarketShare’s global stats report.According to early data shared with ZDNet’s Ed Bott, Chrome OS devices represent a paltry 0.023% of the global browsing population. For comparison’s sake, that’s around one fifth of Windows RT’s slice of the pie, which currently sits at 0.12%.The big difference, of course, is that Windows RT devices have only been on sale for a couple of months. Chromebooks first hit the streets in June of 2011. At 0.12%, Windows RT is an abject failure. Chrome OS, on the other hand, is going to kill Windows (at least according to some). Those predictions may yet come true, but it’s going to be a very long, drawn-out battle if the present pace continues.Then again, perhaps the fantastically pricey Chromebook Pixel will help kickstart sales. Leading by example seems to have worked out OK so far for Windows RT, after all, with the Surface helping Microsoft’s touch OS leapfrogging Chrome on the charts in just four months.Make no mistake — Google didn’t think that success would come overnight. Still, after two years surely the company would like to have notched at least a full percent.Being a bigger disappointment than Windows RT has got to sting. But with the power of the world’s most popular web browser, search engine, and video site behind the brand, don’t feel too bad for Chrome OS. It’s obviously still going through basic training before the real assault begins.