Rigorous evaluations of IPS suggest that 60% or more of IPS clients obtain competitive jobs, compared to about 25% of those who receive other types of vocational assistance. One way of interpreting this finding is that approximately 25% of clients who express an interest in competitive employment will succeed in obtaining a job in diverse and ineffective vocational programs or even without any vocational services, but IPS helps an additional 35% of the target group who otherwise would remain unemployed. The finding of a large and statistically significant beneficial impact of IPS is robust, upheld in all 15 studies. The effectiveness of IPS is also suggested by other measures of competitive employment outcome, including time to first job, job duration and total hours employed during the follow-up period. Most IPS clients work part-time, typically half-time; about two-thirds of those who obtain competitive employment work 20 hours or more per week. Few IPS clients work full-time, likely due to preferences, limited stamina, and/or fear of losing health insurance or other benefits. Consistent with the principle of rapid job search, the time to first competitive job for IPS participants is nearly 10 weeks sooner than for controls. The mean length of time to first job for IPS participants (19 weeks) is, however, still lengthy for a model that prescribes rapid job search.