The Massachusetts unemployment rate in September fell to 3.6 percent, its lowest level since June 2001.

The Executive Office of Labor and Workforce Development reported Thursday morning that Bay State employers added 5,100 jobs in September, helping to lower the jobless rate from 3.9 percent in August. The jobless rate in Massachusetts has fallen 1.2 percent over the past year.

"The rate has fallen dramatically in the last two months, 3/10 of a point this month, and 2/10 of a point the month before. While these are preliminary estimates, this is very good news for the Commonwealth," Secretary of Labor and Workforce Development Ronald Walker II said in a news release. "Over the year, jobs are up 63,800."

While new jobs and more people working have historically pointed to surges in state tax collections, Gov. Charlie Baker and the Legislature have spent the past nearly two years chasing after budget deficits largely tied to overly optimistic estimates of revenue collections.

The contrast between jobs and unemployment data and revenue collections has forced policymakers to research underlying activity.

The U.S. unemployment rate of 5 percent is "considerably higher" when considered through the lens of the worker participation rate, which differentiates between those employed and actively looking for work and those who are unemployed or not actively pursuing work, according to Congressman Richard Neal.

The worker participation rate was about 66 percent in 2006 and 2007 but has fallen steadily since and rested at 62.9 percent in September, according to the federal Bureau of Labor Statistics.

"The worker participation rate needs to be the focus," Neal told the News Service last week. "The unemployment rate does not take into consideration the number of people who are working two jobs, but not counted, or those who want to work and can't find a job or those who took Social Security disability claims at the beginning of the recession. They're not likely going back to work. And those who took the Social Security draw-down at 62—they're not going back to work. So these are people who have just left the workforce and it's estimated that there are 8 to 9 million of them. So that's the key."