For every 100 persons arrested for a violent felony in 1994, an estimated 23 were convicted. In 2004, the rate was 31 persons convicted for every 100 persons arrested....However, only 69% of convictions in murder cases are secured through a plea bargain.
The average sentence length to State prison for a violent felony declined between 1994 and 2004(from 10 years to 71/2 years). However, felons sentenced for a violent felony in 2004 were more likely than those sentenced in 1994 to serve a larger proportion of their sentence before release.
Also, according to the DOJ, 95% of federal convictions are secured through a plea bargain. (The percentage of those garnered through cooperation agreements is unknown to me; I'm searching through data, but haven't found anything good yet.)