Something big is going to have to change in the U.S. construction industry, where employers are adding jobs faster than they can find people to hire.

Construction companies keep on advertising new jobs, but hiring has hardly budged during the recovery, new figures released Wednesday by the Bureau of Labor Statistics show.

While construction job openings were up nearly 400 percent since the official end of the recession through June, actual hiring rose just 10 percent.

The pace of job creation has enough to send the unemployment rate for construction workers plummeting, to 4.5 percent in July. That's down a full percentage point from the year before, and three percentage points from 2014. Construction unemployment rate soared above 25 percent during the worst of the housing bust.

With so much unfulfilled demand for labor, it's a good bet to expect that construction wages will start rising to entice more workers into building. Although there are now 6.9 million construction workers in the U.S., up nearly 2 million since the depths of the crisis, the pre-recession high of over 8 million is still a ways away.

In fact, that's starting to happen already: Employer costs for construction workers were up 2.7 percent annually in the second quarter, according to a separate Bureau of Labor Statistics data set, a significant acceleration.

What's happening in the construction industry is just a particularly intense example of what's happening in the U.S. labor market as a whole. While job openings are up nearly 140 percent during the recovery, actual hiring has risen just 40 percent.

The vacancies and hiring statistics released Wednesday were taken from the Job Openings and Labor Turnover Survey published by the Bureau of Labor Statistics. Although the survey is released a month after the monthly jobs numbers, economics and government officials follow it closely because it contains fine-grained detail that the jobs numbers don't and can provide clues about the underlying health and dynamics of the jobs market.

Recent payroll job growth has been relatively strong. Over the past three months, the economy has averaged 190,000 new jobs, and the unemployment rate has held below 5 percent.