Terry Segerberg knows when the construction industry is about to slow down or take off — before the builders do.

She knew it six months before the housing bubble popped and the industry laid off a couple of million workers, when she sensed builders moving from new projects to remodeling ones — a sign that activity was ebbing.

And she knows the opposite is happening now, she’s sure of it, has known it for a while: Activity is picking up. Folks are building new things — offices and prisons other non-residential things, mostly — and jobs are almost certain to follow. “We’ve spent the last 18 months prepping for significant growth,” she said last week.

Segerberg is the CEO of Mesa Industries Inc., which sells materials and equipment to construction firms across the country and around the world. She gauges the industry’s health through the orders coming in her door in Cincinnati. In that sense, Segerberg is a critical barometer for the U.S. labor market, which rose (such as it was) and fell over the past 15 years with the fortunes of the construction industry.

The Great Recession took a huge bite out of construction employment, but looking ahead, the industry remains critical to the job market, especially for workers without college degrees. For the foreseeable future, one big reason you’d hire an American worker is to build something here.

The 2000s were a terrible decade for job growth, but they were great for builders. Between 2000 and 2006, at the height of the housing bubble, the country added 900,000 construction jobs; that amounted to one-fifth of all the net jobs created in that time across the economy. But those jobs all vanished during the recession, and then some. The construction industry shed 2.1 million jobs from 2007 to 2010, the equivalent of one-fourth of the nation’s net job losses.

Recently the industry has begun to rebound. The economy has added 500,000 construction jobs in the past four years, and construction spending has increased overall. Private residential and nonresidential building is up from 2010, by more than enough to offset a decline in government construction spending.