Yes you do. Because even if they don't register an achievement, they still show up as part of the total population of possible "achievers". I've verified this f

Yes you do. Because even if they don't register an achievement, they still show up as part of the total population of possible "achievers". I've verified this from my own stats as a developer and that of other developers. As long as any portion of the userbase registers some achievement data, you can (well, could) get scarily accurate stats. The only "inaccurate" part is that the stat you're measuring -- "achievers" -- doesn't exactly correlate to any stat we directly care about, like sales. In all the measuring I did against known private sales data, it was always higher than the # of people who had downloaded the game, and the # of people who had played it for at least 1 minute. My best guess is family sharing inflates the "achievers" stat.