Since 2006, his steals / caught stealing numbers are 41/4, 44/0, 15/2, and 14/0 (so far this season). His ERA+ in that time frame has been 117, 129, 97 and 68 (very small sample size).
Despite his lack of ability to keep runners from stealing, he's been pretty successful. In the FanShot discussing the latest article from Fangraphs, I asked whether holding runners might limit Young's effectiveness in other ways - perhaps distracting his attention from the batter - similar to how you can't just tell a power hitter to strikeout less and assume the rest of his game will be unaffected.
Sky responded by wondering how important controlling the running game actually was. I'm quoting myself here (and keep in mind this was back of the envelope type stuff, so not very precise):