I haven't yet. Don't confuse the provision of the service with how you pay for it. There are a number of these programs that are very successful.
I gave you the example of a program in Maryland called the public safety compact, which was designed to reduce recidivism and prevent offenders from returning to prison. It has been in place for three or four years. It has been paid for with a social impact bond.
The program has been extremely successful compared to control groups. It has reduced the number of offenders returning to prison by a wide margin. But the Department of Public Safety and Correctional Services has decided not to renew the contract through this mechanism because they're not achieving the savings they expected; they're paying 60% of the total fixed and variable costs to this provider for this service. They think they can simply contract directly for this service from the provider without the financing component and have a very successful program.
Rikers Island in New York also seems to have a very successful program right now, but the question is, how do you pay for it? The programs can be very successful. You don't necessarily have to have a third-party financier with a rate of return.