COSA participants from a national replication sample (Wilson, Cortoni & McWhinnie, 2009), had 83% less sexual reoffending (1 vs. 6), 73% less violent reoffending (4 vs. 15), and 71% less reoffending of any kind (5 vs. 17) than the matched comparison group.
Furthermore, in looking at the actual total number of new charges and convictions incurred by the two groups (as opposed to the number of offenders who recidivated), the COSA group incurred 74% fewer charges and convictions (17 vs. 73) than the comparison group. Wilson, R.J., Cortoni, F. and McWhinnie, A.J. (2009).
Circles of Support & Accountability: A Canadian National Replication of Outcome Findings. SEX ABUSE: A Journal of Research and Treatment 21(4) 412-430.