Probability of finding life-supporting exoplanets We've found over a thousand exoplanets by now, but how many of them could support life? What percentage of newly found planets are potentially life-harbouring? Or haven't we found any exoplanets that meet these criteria yet?
The question can be rephrased into: How many exoplanets have been found that could harbour life? As of early May 2015 the number appears to be about 30, see the Habitable Exoplanet Catalog on the Planetary Habitability Laboratory's web site.

You should also note that exoplanet detection methods will bias this sample in favour of Super-Earths.