The total number of registered voters in Massachusetts has fallen slightly, even while the ranks of those not choosing either major political party are growing.

Secretary of State William Galvin announced Wednesday that 4.15 million people were registered to vote in next week’s party primaries.

Of that, 1.5 million are Democrats, or 37 percent of the total. Another 471,000 are Republicans, equalling 11.4 percent of the total. And 2.1 million – or 51.4 percent – are unenrolled in any party.

In the 2008 general election, there were 4.2 million registered voters. Some 37 percent were Democrats, 12 percent were Republicans and 50.75 percent were unenrolled.

Following the Sept. 14 primaries, Massachusetts residents will have another chance to enroll for voting in the Nov. 2 general election.