John Oliver did a piece on public defenders that talks a lot about plea bargains, amongst other problems.

https://www.youtube.com/watch?v=USkEzLuzmZ4

Here's a study from the Department of Justice:

https://www.bja.gov/Publications/PleaBargainingResearchSumma...

According to the Bureau of Justice Statistics (2005), in 2003 there were 75,573 cases disposed of in federal district court by trial or plea. Of these, about 95 percent were disposed of by a guilty plea (Pastore and Maguire, 2003). While there are no exact estimates of the proportion of cases that are resolved through plea bargaining, scholars estimate that about 90 to 95 percent of both federal and state court cases are resolved through this process (Bureau of Justice Statistics, 2005; Flanagan and Maguire, 1990).

> As prosecutors have accumulated power in recent decades, judges and public defenders have lost it. To induce defendants to plead, prosecutors often threaten “the trial penalty”: They make it known that defendants will face more-serious charges and harsher sentences if they take their case to court and are convicted. About 80 percent of defendants are eligible for court-appointed attorneys, including overworked public defenders who don’t have the time or resources to even consider bringing more than a tiny fraction of these cases to trial. The result, one frustrated Missouri public defender complained a decade ago, is a style of defense that is nothing more than “meet ’em and greet ’em and plead ’em.”

[1] https://www.theatlantic.com/magazine/archive/2017/09/innocen...