Employees at two Starbucks in Massachusetts have voted to join a union. There are 9,000 or so Starbucks. More of them in the state and other states are considering unionizing. Is a revival of unions in the private sector beginning?

Baristas at the two locations first petitioned to unionize in December, inspired by similar action at cafes in Buffalo, New York. A total of 15 Massachusetts Starbucks — and nearly 200 across 29 states — have since taken steps to form a union.

Employees at two Boston-area Starbucks cafes voted unanimously to formally unionize Monday afternoon — a first for the coffee giant in Massachusetts.