In some quarters there is still debate over the extent of the impact of the shale revolution on the US economy. While the evidence can be murky, common sense says the impact is large—but perhaps not as large as those in the industry might expect.

“The oil and gas industry is about 1% of the US economy today, and that is something that stops my oil and gas colleagues,” said Stephen Gallagher, managing director and head of research for Societe Generale in the Americas.

“By region, by company, by sector, the numbers can be quite large, in the billions of dollars, but in aggregate it's a small percentage of US GDP,” he said in a recent presentation to the Houston Energy Finance Group.

“But the US economy would be in a lot worse shape if not for higher oil and gas prices encouraging new supplies to come online,” he said. “While we are looking at tens of billions of dollars from drilling, production, new pipelines and so on, some of this economic impact is substitution for losses elsewhere in the economy, and not a net gain—like replacing the coal producers …,” he said.

So, how much does the oil and gas industry contribute to GDP? Production growth adds about 0.1% to GDP growth, while added consumer purchasing power, thanks to low gasoline and low electricity prices, adds 0.1% to 0.2%. Infrastructure gains and “onshoring”of manufacturing, and more US exports, each adds another 0.1%.

Still, 0.1% of GDP is $15- to $20 billion of GDP gains per year in the US economy, and $330 billion over 10 years, if the oil and gas industry were to add 0.2%.

“These are measurable benefits,” Gallagher said, adding that he thinks these forces are beginning to transform the macro economy.

He likened it to the effects of the Internet and the percent of GDP that it added to the economy 20 years ago. At first, the Internet added only a few percentage points per year to GDP, but today, the cumulative effect is big.

“I think oil and gas will have a similar effect, but not as large as the Internet has, adding maybe three-tenths of a percent to GDP, because it is not so much that it is adding something new, as it is a substitution [for declines in other industries].”

But, the compounding effect of a few basis points over time is a strong story, he said.

“What's going on in natural gas is transformational,” he said, citing pending LNG exports, the decline in energy consumption, conservation and enhanced efficiencies in energy use. “We are still adjusting to higher commodity prices.”

Just recently, the Multi-State Shale Research Collaborative indicated that the jobs aspect of the shale boom has been overstated. Lou D'Amico, president of the Pennsylvania Independent Oil Gas Association, took offense.

“Well over 1,100 jobs have been saved at refineries in Philadelphia and Marcus Hook thanks to natural gas being produced in counties in the Commonwealth,” he said in a statement. “Williamsport was recently recognized as the country's seventh-fastest-growing regional economy, with more than 85 new businesses opening in the area in a span of 18 months. The per-capita personal income in Washington County increased from $29,138 in 2001 to $46,237 in 2011, an amount almost 10% higher than the state average.”