These numbers for ending out 2016 put the Linux market-share at 0.87%, or down 0.01% compared to November 2016. Their numbers didn't show too much movement while macOS dropped by 0.15% and Windows went up by 0.2%, or continuing to put the overall Windows Steam marketshare at about 95.6%.
While 0.01% change isn't too much, at this time last year the Steam Linux gaming market-share was 0.97%, or 0.1% higher. These numbers remain much lower than when Steam for Linux initially debuted and was closer to a 2% level. You could argue that Steam overall has picked up many new customers in 2016 so that the overall Linux market-share hasn't decreased in the number of Linux gamers, but it's not keeping up to other operating systems with Windows 10 not turning out to be a doomsday scenario some folks had once envisioned and SteamOS / Steam Machines haven't been some big white knight nor the other Linux desktop initiatives really panning out.
Those wanting to dig through the Steam Survey numbers for December 2016 can find them here. Feel free to debate them in the forums and share your thoughts on the Linux gaming/desktop marketshare movement.