The One Number That Mattered Most in the March Jobs Report

— -- U.S. businesses added 215,000 jobs last month and the unemployment rate ticked up to 5 percent in March from 4.9 percent in February. But there was just one number that mattered most to investors: the labor force participation rate.

This rate shows the labor force as a percent of the population. In other words, it helps economists understand the number of civilians ages 16 and older who are employed or who are actively looking for work. Last month the labor force participation rate was 63 percent, up from 62.4 percent in September. The rate, which is now at its highest level in two years, has slowly increased as more Americans are finding jobs.

A stronger labor market could influence how the Federal Reserve moves on interest rates. Federal Reserve chair Janet Yellen said in a speech on Tuesday that the central bank will move cautiously on raising interest rates this year, in part due to global uncertainty.

A low labor force participation rate could signify to the Fed that there is slack in the workforce, according to Mark Hamrick, senior economic analyst with Bankrate.com. Last month, the Fed said in its economic projections that it may have two rate hikes this year, compared to an original forecast of four at its December 2015 policy-making meeting.

But Hamrick believes a large rise in labor force participation is unlikely in the immediate future, and he remains skeptical that the Fed will raise rates at its April meeting.

"For now, it doesn’t appear that Yellen and most of her [Federal Reserve] colleagues have sufficient confidence to raise rates right away," Hamrick said.