Four years after the last recession ended, there are still about 4 million Americans who have been unemployed more than six months and are actively looking for work, said Andrew Sum, director of Northeastern University’s Center for Labor Market Studies. That number, Sum added, does not include millions more frustrated job seekers who have given up job searches and are no longer counted by the government as unemployed.

“The longer you are unemployed, the more difficult it is for you to become reemployed,” Sum said. “And these are the largest numbers in our history by far.”