The tax increase, the first since the 2009 calendar year, will help cover a $5.75 million funding gap in a planned overhaul of the county's emergency system, officials said.
They said last month that they did not want to increase taxes on property owners, but, confronting mounting pension and health-benefit costs, they would have been forced to cut services otherwise.
Commissioner Ryan Costello noted in a statement that the county "still has one of the lowest tax rates" among counties in the region, even with the increases. He said the county had undertaken streamlining measures in the last three years, operating with 200 fewer employees than in 2009, to save money.
County departments had been asked to cut 3 percent across the board, Terence Farrell, the commissioners' chairman, said last month.
"Everybody's been asked to tighten their budget. We're not closing the libraries and we're not closing the parks," Farrell said.
While the county's required pension contribution has increased by about $1.5 million this year, interest income has shrunk from $11.7 million in 2002 to an estimated $208,700 in 2013.
Contact Aubrey Whelan at 610-292-8112, email@example.com, or on Twitter at @aubreyjwhelan.