The Massachusetts unemployment rate dropped to 3.9 percent in August, the first time it has fallen below 4 percent in 15 years.

The Bay State added 5,900 jobs in August and 5,800 jobs in July, which is a smaller amount than the initial job estimate for July. As the state's job base has grown state tax revenue growth has been slow, falling $36 million below reduced expectations so far in fiscal 2017.

The last time the unemployment rate dipped below 4 percent was August 2001, a period at the tail end of the dot-com boom of business rushing onto the internet and immediately before the Sept. 11 attacks that ushered in years of war.

Last month's unemployment rate is nearly a full percentage point below the 4.8 percent unemployment rate in August 2015.

There are 30,300 fewer unemployed residents and 73,000 more employed residents compared to August of a year ago, the Office of Labor and Workforce Development reported on Thursday.