U.S. oil and natural gas extraction jobs began inching up in parts of the country in late 2016, and it can’t come quickly enough as the tight labor market apparently already is affecting onshore drilling efficiencies as operators raise more rigs.

The Bureau of Labor Statistics (BLS) on Friday said the oil and gas sector began to get back to work in November. BLS data issued last Friday reported jobs information for combined oil/gas extraction and support sector jobs through November. BLS also provided extraction jobs data only through December.

In November, the report showed an increase in combined extraction and support services jobs of 3,300 to 384,300, the first uptick since September 2014, when sector employment peaked at 536,100. Nationwide, extraction jobs only in December fell by 1% (1,300) to 172,400 after gaining 1,400 in November, in part because of seasonal factors.

Operators may be returning to work, but they appear to be finding it difficult to fill positions, according to anecdotal evidence compiled by Evercore ISI. Field-level commentary suggested that the labor squeeze already is affecting crew efficiencies, said Evercore’s James West.

“From our discussions with service company management and in reaching out to ex-oilfield workers that had overwhelmingly sworn off the coveralls for good, we already understood that labor attrition would be a hindrance to continued efficiency gains in North America,” West said Monday.

“This past weekend, we once again reached out to several boots on the ground to get an operational update on the status of the upturn,” he said. “Surprisingly, the labor and equipment squeeze has already begun to take its toll with a faster-than-expected ramp in activity; even without an appreciable increase in the number of incremental crews, the existing market is struggling to keep up with current demand.”

Last month the Federal Reserve Bank of Dallas (Fed) said oil and gas labor market conditions had turned positive for the first time in 2016 during the final three months of the year. The Fed’s business activity index rose 40.1 from 3Q2016’s 26.7 reading.

In its latest jobs report last week, the Dallas-based Fed said improving conditions were affirming an “increasingly positive outlook” for the Houston area, the acknowledged U.S. energy capital, but it said a “broad-based recovery remains elusive.” Total employment in the metropolitan area is growing “moderately,” the Fed said.

“Oil prices and the rig count are recovering, but energy jobs have yet to follow. While many sectors have improved since mid-year, the construction and manufacturing sectors continue to lose jobs. Altogether, Houston is showing signs of improvement and the outlook is becoming more positive.”

In the most active drilling area in the country, the Permian Basin, labor market conditions “continue to be bumpy,” even with increases in crude oil production, according to the Fed.

Halliburton Co. affirmed in late December it is ready to hire more than 200 people in the Permian Basin for “all of its product service lines and support functions.”

Former oil and gas workers laid off in the downturn may not be too eager to return to the oil and gas fields, according to an ongoing study by the University of Houston (UH). Almost 90% of people surveyed who lost their jobs during the bust remain unemployed or have opted to leave the oil and gas sector entirely.

The UH study is focused on oil and gas industry workers who have lost their jobs within the last two years.

About 25% of the 720 respondents so far have found work outside the energy industry, but more than 60% remain out of work. Only 13% have returned to a job in the oil and gas sector.

Of former employees who have responded, almost three-quarters (70%-plus) said they are nervous about the future of the industry. More than half (55%) said they’re considering never taking another job in the oil and gas field. Almost 66% also were unhappy about how the layoffs were handled by their former employers.

According to UH’s Bauer College of Business, oil-related jobs are among the “most skilled and highly compensated” in Houston. Oil-related job losses in the metro area reached 47,700 in 2015 and slowed to 25,900 in the first 11 months of 2016. The contraction in the Houston area for jobs related to oil production, oilfield services, machinery/fabricated metals, wholesale trade and some professional services was the “largest number of oil jobs lost to any cyclical event since 1990.”