Fed chair eyes policy experiment to squeeze labor-market slack

Low rates could boost demand, increase hiring and investment

Harry Elanko is one of the American workers in Federal Reserve Chair Janet Yellen's petri dish.

Elanko, 62, from Fairfax County, Virginia, is holding down two part-time jobs as he seeks full-time work. His resume shows years of experience as a business administrator -- the kind of back-office guy who pays the bills and taxes and makes sure everything runs smoothly.

For Yellen, the six million people like Elanko working part-time because the economy isn't strong enough, plus the more than 600,000 who've become so discouraged about prospects that they've stopped looking for a job, signal interest rates can stay low for longer.

Too depressed to even look for work