An analysis published Tuesday found that 90 percent of federal defendants pleaded guilty while just 2 percent went to trial during fiscal 2018.
The remaining 8 percent had their cases dismissed, according to the Pew Research Center.
The Pew analysis of federal judiciary data found that of the 2 percent of defendants who go to trial, 83 percent are convicted, while 17 percent are acquitted.
The analysis notes that 320 of 79,704 total federal defendants went to trial and won their cases.
The percentage of federal defendants who go to trial has decreased over the past 20 years, as 7 percent of defendants went to trial in fiscal 1998, according to the study. Even though there are more federal defendants now, 4,710 went to trial in 1998, compared with 1,879 in 2018.
Trial rates also varied based on what type of offense was alleged.
The report found that less than 1 percent of immigration cases went to trial, compared with 2 percent of drug offense cases, 4 percent of property offense cases and 7 percent of violent offense cases.
Several explanations have been given for the shrinking number of criminal trials, but according to the report, one common explanation is that those who go to trial can face harsher sentences.
According to Pew, there is not standardized data on state court trial rates, but they are also generally low. Pew's report said that in many state courts in 2017, fewer than 3 percent of criminal cases went to jury trials, citing information from a National Center for State Courts database.