If you’re pessimistic about the stature of the United States in an ever-shrinking world – and a host of studies says most Americans are – Joel Kotkin might be just the tonic you need.

The  author and noted expert on global, economic, political and social trends sees the prospects of the United States on much better footing than many of our economic rivals. Why? A relativly young demographic base, ample resources and plenty of aerable land.

Kotkin, who spoke in Nashville before an audience at ecnomic development organization Partnership 2020′s annual meeting, projects the U.S. population will likely reach 400 million people by 2050 (Yes, he is author of the book The Next Hundred Million: America in 2050) That will come from rising birth rates but mainly from an in-migration of people from other countries, giving the U.S. a supply of younger workers and bringing with it new opportunities for entrepreneurhsip and innovation.

By contrast, he says Europena and Asian countries will see stagnant or declining populations, which will leave them with a shortage of workers to support their large social welfare programs.

“We have a problem with aging, but not as much as others,” he said.

In Kotkin’s view, regions in the U.S. with between 1 million and 2.5 million people are better positioned to capture that growth, especially those in the South. Metros such as Raleigh, Austin, Charlotte and Nashville were among the fastest-growing metros in the United States between 2000 and 2010.

Kotkin maintains that economic trends over the last few years are countering the notion that people will make location decisions based on where they want to live rather than where they can work.

“People are going to where there are jobs,” he said. The “sweet spot” is an area that is creating jobs and has attributes that make it attractive as a place to live. “In this era of the Internet and air travel you don’t just have to be in one place,” he said. “You can have the amenities of a big city in a smaller place.”

Among the trends influencing where people are moving:

Economy: “People are going to where there are jobs.”

Affordability, particularly in housing: Even among Millenials – that cohort born in the early 1980s – who may have been attracted by large cities tend to relocate to places where they can afford to buy a home.

Elbow room: Regions that offer lower population densities and suburban/exurban housing options. Kotkin disputes the notion that younger people are abandoning the suburbs for denser urban areas, and cites research showing the 25-34 population grew by 1.8 million in the suburbs between 2000 and 2010 while declining by 1.3 million in core cities. “They grew up in the burbs.” he said “When 20-somethings get older, they do things like marry, start businesses, settle down and maybe start having kids.”