The oil and gas industry created more than 4,600 construction jobs in the Marcellus region in 2013, with more expected this year, according to a recent study by the University of Illinois.

“Natural gas exploration has been a strong engine of job growth,” according to the study.

Construction and maintenance spending reached $5 billion in the region last year, growing by 61% over 2012, and $6.5 million has already been committed for 2014, according to the study.

“Over the last six years, approximately 35.8 million labor hours came from major plant capital and maintenance work in the oil- and gas-related indirect industries with an annual growth rate of 30.7%,” according to the study. “The year 2013 reached an all-time high with over 9 million labor hours recorded. This represents a 40% increase over 2012.”

The study included employment activity with direct, indirect or no relationship to Marcellus Shale development in Pennsylvania, Ohio, West Virginia, Maryland and Virginia.

Activity classified as having a direct relationship with the oil and gas industry included building storage terminals, pipelines and processing plants. Activity with an indirect relationship included plants that use large amounts of natural gas as a feedstock, such as paper mills steel mills, chemical processing plants and power-generation plants. Researchers studied labor hours for 13 trades, including boilermakers, electricians, pipefitters, plumbers and carpenters.

“The build-out of the oil and gas industry in 2013 resulted in an additional 5,500 craft worker jobs. Estimating off the median base wage rates of each craft, over $247 million was paid out to workers in this industry as a result of ongoing construction activities.”

Those in non-shale-related industries did not fare so well. Construction activity there has actually fallen 53.7% since its 2008 peak of 14.8 million labor hours, according to the study.

“Last year, this group of industries only generated 6.6 million hours for the eight trades highlighted in this report. At one time, 7,100 full-time construction jobs were created annually. That number has fallen to 3,300 jobs.”

According to a 2011 study commissioned by API and reported by PwC, oil and gas accounts for 9.8 million jobs, or 5.6% of the total U.S. employment. In addition for each direct job supported by the industry another 2.8 jobs are created elsewhere, according to PwC.