Planners in Baton Rouge have their hands full trying to grapple with the oversights of prior decades, but Mitchell Silver, the chief planning and economic development officer of Raleigh, N.C., spent a few days earlier this week telling planners about what’s coming up.

The United States, he said, is changing in dramatic ways, and planners and developers need to watch demographic trends like investors watch the stock market.

America is getting older, the working-age population as a percent of the total will drop, minority populations are surging and the single-person household will dominate by 2040, he said.

Infrastructure is aging and the unsustainable nature of traditional, sprawling development patterns is only going to get worse. Yet many developers continue to build the homes of yesterday, hoping that people will flock to the suburbs.

“They’re developing a dying commodity,” Silver said, speaking Tuesday at the Center for Planning Excellence’s annual Smart Growth Summit downtown.

The traditional building styles and development patterns persevere, but generations X, Y and Z — primarily Y, which includes those born between 1982 and 1995 — aren’t as interested in yesterday’s housing styles and suburban living. They prefer choice, collaborative cultural environments, diversity and are more purpose-driven than their parents.

“They move to a place without having a job,” Silver said. “Who does that?”

But with the nation’s development patterns in desperate need of a turnaround, generations X, Y, and Z “came just in time,” he said.

If cities don’t have the kinds of housing, culture and public spaces they want, they go where they can find it. And too much development is anticipating wants and needs that are an anachronism.

Silver said 80 percent of young people with a bachelor’s degree were married in 1965, compared to 50 percent now. Unwed births have risen from 5 percent of total births in 1960 to 41 percent in 2009.

Silver said there will be an excess of 25 million single-family homes by 2030 because of the gap between the single buyer and large homes designed for an earlier age.

Silver showed a slide indicating all the parishes in Louisiana that have lost population, with the growth centered around its cities. Slides of other states told the same story: America is becoming more urban, not less, and infill development within cities’ already developed footprints using existing infrastructure is the only way to do it.

“We need to figure out where to build between 45 and 50 million units,” he said.

And it’s not just young people who will fuel the need for walkable communities that are close to their day-to-day needs.

By 2030, one of every five people will be older than 65, and 600,000 people older than 70 stop driving every year.

Silver, who is also president of the American Planning Association, made the economic argument for denser infill and downtown development.

A downtown high-rise residential tower pays off its infrastructure cost in three years with a return on investment of 35 percent. A 30-acre suburban multifamily complex pays off its infrastructure costs in 42 years, with a return on investment rate of 2 percent, he said.

He also laid out the costs of sprawl, noting the urban service area of Champaign, Ill., generates a tax surplus of $33 million while the sprawled area accounts for a $20 million tax deficit.

Public transportation and mass traffic factors into the picture as well.

By adopting and following the Envision Utah plan, the Salt Lake City metro area will save 4.5 billion in transportation, water, sewer and utility costs by 2050.

Robert Grow, chairman emeritus at Envision Utah, the plan that included a significant investment in rail transit, said planners need to learn to talk to residents, but also listen to them.

He showed how Envision Utah used a technique called value ladders to determine what things are important to the community, and then how better planning can achieve those goals.

Grow showed television spots used to sell the tax that passed to pay for the rail system, focusing on how traffic congestion had eroded the quality of life.

The transit tax won the support of 70 percent of voters in the most conservative county, and the state’s largest anti-tax group stood down.

“We knew our values,” he said, noting that a successful campaign can communicate with people using “their own language in ways you know are emotionally impactful.”

Grow showed photos of two homes — the first homes of his son and his daughter, incidentally. One was a $600,000 house and the other was an $87,000 home. He asked which home was better for a typical college graduate making $30,000 or $40,000 a year?

Affordability, he said, is best explained in personal terms that people can relate to.

Silver spoke to the issue as well, noting he has always made it a point in public dialogue to make sure opposition always realizes what the consequences are to taking no action at all.

“When they say no to something,” he said, “they are saying yes to something else.”