While United States metropolitan areas are economically strong with more than 300 metros experiencing job growth in 2016 and accounting for 95 percent of all the US job gains last year, growth continues to remain uneven, with nearly one-third of metro cities (121) still not having recovered their lost jobs from the Great Recession, according to a report released today by the US Conference of Mayors.

These metros are predominantly older Midwestern communities suffering from the loss of heavy manufacturing jobs and an aging population and infrastructure.

The report further forecasts that by the end of the decade (2020) nearly one in four US metros (88) will have employment levels below their 2008 levels, representing a decade of lost jobs. For some metros, the loss of jobs has been even more prolonged, with 23 cities having fewer jobs today than in 1990. A large number of metros (140 or nearly 37 percent) for the same period experienced annual job growth of less than 1 percent.

Issued during Infrastructure Week in Washington, DC, the mayors’ report also points to infrastructure spending as an economic tool that holds the promise of generating job growth across these metros. Such investment, if funneled directly to metro regions, can create jobs faster, relieve congestion, decrease costs to businesses and increase productivity, all of which further accelerates growth.

“Some of the oldest infrastructure is in the Rust Belt metros, which our data show have lagged the national recovery and expansion,” said Mick Cornett, mayor of Oklahoma City and president of the US Conference of Mayors. “And while infrastructure investment is not a cure-all, it can provide cities a shot in the arm to help jumpstart their local economies.”

But increased infrastructure spending is also needed in high growth areas. The report’s findings project that over the next 30 years, the US metro population will grow by 66.7 million people, almost all of the nation’s total population growth. By 2047, 72 metros will have population exceeding one million, compared to only 53 in 2016. In addition, five metros will have over 10 million people by 2047—whereas only two currently meet that benchmark. And as the metro areas grow, so will traffic congestion.

From 2013 to 2014, 95 of the nation’s largest 100 metros saw increased traffic congestion, up from 61 from 2012 to 2013. The price tag associated with this congestion, which is the value of wasted time and fuel, is estimated at $160 billion in 2014 for US urban areas, or $960 per commuter.

Mayors maintain that infrastructure investment in roads, rails, bridges and other forms of transportation will help relieve the bottlenecks impeding economic expansion, noting for example, the 4.8 billion hours of travel delay Americans experienced in 2014.

“Infrastructure dollars should also be directed where the potential returns are greatest,” said Louisville Mayor Greg Fischer. “Clearly, population and economic projections indicate that growth in the United States in the coming years will largely be in cities and their metropolitan areas. If we ignore these trends without preparing for future growth, we will face unnecessary challenges to human, environmental, and economic health.”

US metros contribute 91 percent of the production of goods and services that make up the nation’s total gross domestic product (GDP). Since January 2009, 315 metros, 83 percent of the total, gained jobs. And twelve of those metros, led by Provo at 29 percent and Austin at 27 percent, exceeded a 20 percent growth rate over the 2009-to-2016 period.

“As we look toward the release of the federal budget, mayors are hopeful, as the president promised, that an infusion of federal infrastructure dollars to our cities and metro areas is forthcoming,” said US Conference of Mayors CEO and Executive Director Tom Cochran. “Anything less will be wholly insufficient to meet the infrastructure needs of the country.”