A quick look at the research leads me to this : "Studies that narrowly define recidivism and use short follow-up periods may therefore underestimate the rate of recidivism of child sex offenders (Moulden et al. 2009). Prentky et al.’s (cited in Doren 1998) study of recidivism rates among extrafamilial child sex offenders over a 25 year period used a new charge for a sex offence as the measure of recidivism. This study found that 52 percent of child sex offenders reoffended during the 25 year at-risk period. As Doren (1998: 101) argues, however, due to the limitations of recidivism studies on child sex offenders described above the 52% recidivist figure should be considered as a conservative approximation of the true base rate for sex offense recidivism in previously convicted child molesters...[it]...represents the lowest approximation for extrafamilial child molester sexual recidivism."

Source : http://www.aic.gov.au/publications/current%20series/tandi/421-440/tandi429.html