Daniel F. McNamara, the president of the Detroit Fire Fighters Association, described the city’s economic growth as “small little pockets” in an otherwise painful cityscape where services like fire protection have shrunk to too few firefighters and too many shuttered fire companies.

“If you’re a hedged investor, this is great,” Mr. McNamara said. “There are lots of attempts at tremendous things going on. But for you and me, has our world changed any? Not so much. There are so many individual tragedies going on.”

No doubt the picture here remains murky and unfinished. For all the talk of a private sector renaissance, demographers say that much of the economic growth remains mostly around the downtown and midtown sections, a small fraction of a vast 139-square-mile city that is otherwise wrestling with vacant homes, empty blocks, darkened streetlights, crime fears and overburdened police officers. While businesses have returned to Detroit, some others have left, and this city’s most essential problem, its swiftly dipping population, demographers say, has yet to reverse itself.

This city grew up around the automobile, becoming home to more than 1.8 million residents by 1950, before the population began sinking along with a decline of manufacturing, wide-scale flight to the suburbs, and the travails of the American automobile industry. From 2000 until 2010, Detroit’s population dropped by 25 percent, the biggest percentage loss during that decade for any American city with more than 100,000 people, aside from New Orleans, which had been pummeled by a hurricane. About 707,000 people live here now, by recent estimates, though some demographers say the city has already lost more residents.

But so much misery also brought newcomers: out-of-town investors who learned of properties for sale at prices unimaginable in other cities and young entrepreneurs, artists and musicians who said they valued Detroit, in part, for its grit and its seemingly wide open spaces, the very elements that had made some people flee. Business incubators, like TechTown, began emerging, and Michigan business executives began reinvesting in the city, among them figures like Dan Gilbert, the founder of Quicken Loans, who has bought building after building downtown.

Meanwhile, Detroit’s car companies have experienced what had once seemed like the unlikeliest of comebacks after the financial crisis. General Motors and Chrysler emerged from bankruptcy filings and government bailouts to far more upbeat signs — and with investments in Detroit. Not long ago, Chrysler moved its regional marketing team into a downtown building here, and an assembly plant in the city, Jefferson North, was retooled to produce a new version of the Jeep Grand Cherokee sport utility vehicles, among the company’s hottest sellers.