Massachusetts, which last year passed laws instituting reforms across the criminal justice system, has the lowest incarceration rate in the country, according to a new report.

After a 5.4 percent decline in its prison incarceration rate from the end of 2017 to the end of 2018, Massachusetts had a prison population of 8,692 people, or an incarceration rate of 126 people per 100,000, according to the Vera Institute of Justice's "People in Prison" report.

Louisiana had the highest rate, at 695 people per 100,000 residents, followed closely by Oklahoma, at 683.

Massachusetts also had the fifth largest decline in prison populations between 2017 and 2018, the report found. Missouri, at 7.1 percent, posted the largest drop.

Overall, the Vera Institute estimated there were 1,471,200 people in state and federal prisons across the country at the end of 2018, down 20,000 or 1.3 percent from 2017. Most of those -- nearly 1.3 million -- were incarcerated under state jurisdiction, with 179,900 in the federal prison system.

The report said the nationwide decrease "was driven by the large decrease in the number of people in federal prisons, as well as greater than 5 percent declines in incarceration rates in seven states," including Massachusetts.

Prison populations dropped in 39 states last year, the report said.

The incarceration rate in Massachusetts fell from 177 out of 100,000 in 2008 to 126 in 2018, according to the Vera Institute, which also tracked a 23.8 reduction in the state's prison population over the same time period.

The Bay State's incarceration rate has been among the lowest in the country for years, though justice reform advocates have said it is nonetheless well above the level it was at decades ago.

When Sen. William Brownsberger introduced criminal justice reform legislation on the Senate floor in October 2017, he said the rate is "four or five times" what it was 40 years ago.

In April 2018, Gov. Charlie Baker signed a version of that bill into law, saying it "probably has over 100 separate elements that represent a change in the way business is done here in Massachusetts."

The reforms -- which address bail and diversion programs, along with repealing some mandatory minimum sentences -- range "all the way from the beginning of policing all the way through corrections and all the way back into the runway associated with return to society," Baker said at the time.

The same day, Baker signed a separate law that allows inmates to reduce the time they spend in prison by participating in re-entry programming. That law was the product of a review by the Council on State Government Justice Center. State leaders contacted the Justice Center in 2015, asking for an analysis that would help them "better understand how we can further reduce recidivism and enable successful re-entry, and whether we can further reduce our prison and jail populations through early release programs while ensuring appropriate punishment and preserving public safety."

In addition to its prisons, Massachusetts has a network of county jails and houses of correction that house people serving terms of 2.5 years or less. County sheriffs run the jails and houses of correction.