The United States is one of the only rich countries not requiring employers to give their workers paid time off when they’re sick. It has become an urgent issue for more Americans because of the coronavirus outbreak.

Citing the crisis, Democrats in Congress are trying to pass a new version of a sick leave bill that has been stalled in Congress since 2004 — and expand it to add 14 days of immediately accessible paid sick leave in the case of a public health emergency.

An economics study released Monday offers an idea of what might happen if the bill passed. It’s the biggest study of the effects of state sick leave laws in the United States. In states that mandated sick leave, it found, fewer employees worked when sick. On average, they took two additional sick days a year. And the cost to employers who began offering sick leave after the laws passed was relatively small.

“Right now, the experts are telling people: Stay home if you’re sick,” said Senator Patty Murray, a Democrat from Washington and a sponsor of the new bill. But many workers, including those in the service industry, cannot follow the advice without losing a paycheck, she said. “That’s why paid sick days are such a critical part of this response.”