By far, most.
The conservative estimate seems to be that over 90% of cases end in guilty pleas. The United States Courts website estimates that more than 90% of federal cases resolve this way. A 2012 New York Times article reported that 97% of federal cases and 94% of state cases end via plea bargain.How many criminal cases actually go to trial? | Nolo.com
Yeeesh.... Way more than I thought.