Offhand, I don't know.

It's most relevant at parties and large social gatherings where I don't know anyone, and I don't really think in terms of percentages-of-people in such situations so much as how quickly I find someone worth talking to.

Over 95% of the time, I'd say the result is a little bit of chitchat followed by the person and I both talking to someone else. Whether that's responding well, poorly, or neutrally I don't know; that seems to be the default condition at parties.

Less than 1% of the time, the result is the other person's eyes lighting up in what I've come to label the "oh look, one of my people!" expression, and I make a new friend. Probably not much less than 1%, though.

(By way of establishing scale, I'd say I try this ~50 times in a given year... I'm not a terribly outgoing guy, and generally prefer to hang out in smaller groups or just stay home with my husband, but I'm reasonably socially ept when I do go out.)

That said, I also have a reputation in my social circle for being kind of intense and a little out there, but interesting to talk to if you're interested in, well, talking. Which also creates a second-order effect, where friends introduce me to friends of theirs who share this trait because we'd really enjoy each other, and more generally where my social environment self-selects.