My experience agrees.
In my criminal conviction, the crown had an extremely weak case. No physical evidence, no witnesses. All they had on me was the fact that my victim had plead out to assaulting me six months earlier,a witness who could state that I planned on returning the favor, and obviously I had no alibi. My lawyer gave me 70-30 odds that we would win at trial, but pointed out that if my victim died before the trial, I would be facing murder charges and possibly life in prison instead, so a deal was probably wise. (My lawyer was right, he died about two weeks after I was sentenced.)
My deal was for two years plus a day (the minimum) for Aggravated Assault. The max sentence was 14 years, and the lawyer believed that the most likely result was 6-8 years. So from one point of view, I got a 85.7% reduction in my sentence, assuming that I was sentenced to the max. However, more realistically it was a 66%-75% reduction in my sentence. My lawyer informed me that this was an unusually good deal, one of the best he had seen in a long career.