A new study by the National Association of Manufacturers puts forward the case for infrastructure investment as a stimulus for economic growth.

Long-term investment will increase employment and grow Gross Domestic Product by 1.3% over the next five years and almost 3% over the next 15 years, according to the study.

There would be a three-to-one return on the investment over the next 15 years, as well as an increase in workers’ take-home pay, the study found.

“The United States is stuck in a decade-long period of decline that will eventually harm job creation, future productivity and our ability to compete head-to-head with companies all over the globe,” said NAM president and CEO Jay Timmons in a statement.

“Manufacturers call on Congress to consider this sobering data as it acts to fulfill its well-established responsibility of facilitating commerce in the United States,” Timmons said.

“We need legislation passed to help fund transportation and infrastructure.”

The study comes as Congress moves toward the next phase of the ongoing political struggle over how to preserve and improve the national transportation infrastructure.

Earlier this year legislators punted the key question of infrastructure funding with a bill that maintains the federal transportation program as is until next May.

While some in Congress are agitating for funding action during the lame-duck session following the November mid-term election, others would rather see drastic cuts in federal fuel taxes and devolution of the federal transportation program to the states.

U.S. manufacturers are aligned with the business community at large, including trucking interests, in support of robust reinvestment in infrastructure.

The NAM study found that investment in all infrastructure, including highways, grew annually during the 50 years up to 2003, but then contracted sharply by more than 1%.

“This investment expenditure has lagged GDP growth by a whopping three percentage points on average,” the study says.

“In total, the volume of public infrastructure investment was 10.5% lower in 2012 compared to 2003, and available data indicate it has fallen further since then.”

The investment decline is even worse for highways and roads specifically – down almost 20% in 2012 compared to 2003, the study says.

The effect is that the U.S. is not able to gain ground in improving the infrastructure base, the study says.

What’s needed is a more focused and results-driven effort to expand and sustain higher levels of investment, the group said.

“Manufacturers that depend heavily on trucking for receiving supplies and delivering products would benefit the most from this boost to competitiveness.”

The study also says it is not necessary to stick with traditional approaches to funding, delivering and operating infrastructure.

Echoing themes established in recent infrastructure legislation, the study says investments can be tied to net social benefits and can be made more efficient by improving environmental processes. Also, there is a place for private as well and public investment and management.

“Widespread access to high-quality infrastructure is indispensable to the United States’ economic development and standard of living,” the study says.

“A more focused and outcomes-driven infrastructure effort is needed.”