I do actually know a fair share of people using Linux in my social circle, but a lot of them uses both windows and Linux. My family uses Linux for their private devices, as that was a requirement to get my technical support. And an increasing number of my friends are moving over to Linux.
What I find weird is the sudden increase of 10% (from 18.16% to 29.04%). Like, did everyone get back from vacation after a Linux conversion camp or something?