What are your chances of going to prison?

There was some high drama at this week’s “Second Annual Massachusetts Criminal Justice Reform Coalition Summit,” hosted by MassINC.

As an opener, the state’s top judge, Ralph Gants, offered a full-throated critique of drug sentencing laws in Massachusetts, especially the way “mandatory minimum” sentences block judges from meting out fair sentences. And with no official rebuttal on the agenda, Suffolk District Attorney Dan Conley took time away from a separate panel to strenuously disagree, arguing that district attorneys have their own “wise discretion.”

But perhaps the most arresting moments came in the form of charts, rather than rhetoric — particularly a series of charts showing the odds that men will end up in prison by age 30-34, put together by Bruce Western, a leading expert in criminal justice.

He emphasized three key factors: race, education, and history. In particular, high school dropouts are more likely to be imprisoned. African-Americans go to prison more frequently than whites. And all men have a higher chance of going to prison today than they did 35 years ago.

Put these together, and you can see how dramatically our criminal justice system has changed over time. Back in 1979, African-American men who dropped out of high school had about a 15 percent chance of ending up in prison by age 30-34. These days, it’s nearly 70 percent.

Criminal justice reform has become a hot topic all across the country — partly because of stats like these and partly because prisons are a big drain on state budgets. One reason for optimism is that violent crime just isn’t as big a problem as it once was. Nationwide, the violent crime rate has fallen roughly 50 percent since its peak in the early 1990s. That trend has united groups from left and right around the idea that we can reduce the prison population and keep crime down at the same time.