On December 31, 2008, there were 123,597 felons and civil narcotic addicts on parole in California, a 2.6 percent decrease from 2007. During 2008, 142,954 offenders were admitted to an institution as a new admission or a parole violator and 139,535 offenders were paroled, discharged or otherwise released from custody.
If I am interpreting the data correctly, the following two graphs show the percentage of inmates with a previous parole history out of all prison population (if I'm mistaken, please correct me). If that is the case, it would appear that a bit over 10% of all male prison population and around 12% of the female prison population are in prison for violating their parole terms. The report in itself does not provide us with any information about the type of parole violation that led these parolees to prison, and one would hope that parole reform is shifting toward a focus on serious violations, rather than "technical" violations of terms.
The other bit that merits some attention, however, is the blue line, which, if I understand correctly, depicts the number of entering inmates arrested for new crimes who also happen to be parolees. These numbers say less about the scope of parole enforcement and more about its job providing hope, rehabilitation, and a new future for people leaving prison. Even if we are not rearresting people for parole violations at the rate we thought we were, we're still not doing a great job creating opportunities and incentives that pull people away from new crime.