Oregon’s labor market is growing faster than economists believed, with the jobless rate hitting another record low in July.The monthly unemployment rate was 3.9 percent, according to data out Tuesday from the Oregon Employment Department. That’s the first time it’s been below 4 percent since at least 1976, when the state began keeping comparable records.There’s an important caveat — Oregon reported similar lows last year but revised the numbers upward at year’s end. That could happen again but it doesn’t change the broader trajectory of Oregon’s labor market, which continues to surprise observers with steady growth.“Oregon’s economy is growing faster than previously thought,” state labor economists wrote Tuesday. “Payroll employment figures covering the spring and early summer show bigger job gains than the numbers released four weeks ago indicated.”Oregon added 45,300 jobs in the prior 12 months, expanding the labor market by 2.4 percent. That’s slower than an annual growth rate of 3.7 percent in 2013, but nearly a full percent faster than economists had believed.Another measure of joblessness, the U-6 or “underemployment” rate, is also near an all-time low at 7.7 percent. It measures people who have part-time jobs but would rather be working full time and others who are marginally attached to the labor force.Construction remains one of Oregon’s fastest-growing segments, joined by retail and health care. Government work was the only major category underperforming expectations, shedding 2,200 jobs on a seasonally adjusted basis.