Why is San Francisco doing so much better than Detroit? I know that sounds like a silly question, or at least one that requires no special brainpower to answer. San Francisco is a beautiful city with a gorgeous ocean setting and two world-class universities to attract talented people who find it appealing to live there. Detroit has no scenic advantages and has for most of its life been utterly dependent on one rustbelt industry that has largely left, forcing massive unemployment and poverty. You can make the same inquiry about Seattle and Cleveland, and not have to dig very hard for a solution. Seattle became the take-off city for Amazon, Microsoft and a host of other high-tech businesses that grew up around them. Cleveland had no such luck.

Sometimes the question is a little more complicated. Why, for example, is Chicago so much more successful than St. Louis? That’s a bit challenging, but far from impossible, to understand. St. Louis developed in the 19th century as a city with a river-based commerce. Chicago staked its future on its identity as a railroad town. Chicago won the bet. By the latter half of the 20th century, it was clear that there was room in the Midwest for just one town with “global city” aspirations. Chicago, by that time much larger in population, won that prize as well. Chicago maintained a diverse roster of industries and corporations. St. Louis lost most of its big companies to takeovers. In the end, the Chicago-St. Louis question isn’t really a stumper either.

Occasionally, however, the game becomes more difficult altogether. Why is Philadelphia, by nearly all present-day standards, doing so much better than Baltimore? They are much more alike than either of our previous pairs. They both developed as major port cities, with factories built near the water and rowhouse neighborhoods where the dock workers and factory workers made their homes.

But Philadelphia, despite losing the vast majority of its manufacturing jobs in the last half-century, has maintained a stable population and has actually grown in the last decade. It has a vibrant center and a bustling tourist trade, and the residential districts close to Center City have gradually been restored and become desirable. Baltimore has a picturesque Inner Harbor, but most of its neighborhoods aren’t coming back. It has a viable pharmaceutical industry, but not too much else. It keeps losing population: The most recent tally placed it below 600,000, the lowest number in a century. You wouldn’t expect these two cities to have had such different trajectories. But they have.

I’M NOT THE FIRST PERSON TO RAISE THESE POINTS, but two urbanists from Johns Hopkins University, Matthew E. Kahn and Mac McComas, have raised them in a much more systematic way in their new book, Unlocking the Potential of Post-Industrial Cities. They explore why “some people and places thrive during a time of growing economic inequality and others don’t.” They focus on six older industrial cities and how they are coping in a 21st-century environment. Two of them, Philadelphia and Pittsburgh, are coping reasonably well. The other four — Baltimore, Cleveland, Detroit and St. Louis — mostly are not.

In all candor, I have to say that the authors don’t come very close to providing a definitive solution to the puzzle. Sometimes they make it difficult for the reader to discern which conditions are causes and which are effects. But they raise a host of interesting questions that move the problem at least a few steps further.

The book is particularly incisive when it comes to Baltimore, the city both of them know best. Baltimore has experienced more than a decade of unstable and often corrupt political leadership — in the last 10 years it has had seven mayors, two of whom resigned after pleading guilty to crimes. Its leaders have had to deal with exceptionally stubborn and hidebound public-employee unions, especially police unions.

In 2018, Baltimore recorded an exceptionally high murder rate, second only to St. Louis among the six cities Kahn and McComas examine. It has lived through the street violence that followed the death of Freddie Gray in police custody in 2015. A decade earlier, millions of people around the world had watched the television series The Wire, graphically depicting Baltimore as a city enveloped in drug dealing, street violence and ubiquitous gang homicide.

Baltimore developed as a major port city, with factories built near the water and rowhouse neighborhoods where the dock workers and factory workers made their homes. (Photo: David Kidd/Governing)

Kahn and McComas do not devote much attention to the question of racial demographics, but it is hard to avoid. Baltimore is 62.8 percent African American and Detroit is 79.1 percent Black. They are the most heavily African American of the six cities under examination. Pittsburgh and Philadelphia have the lowest percentages: 23 percent and 43 percent, respectively.

I don’t wish to draw any simplistic conclusions here, but it seems to me that a city widely perceived to be overwhelmingly Black is certain to suffer, even if unjustly, when it comes to population, immigration and overall attractiveness to newcomers. The Wire was great television, but there is no question that it wrote a nearly indelible stain on the reputation of the city where it took place.

It would be a serious mistake, however, to attribute all or even most of the troubles of the faded industrial cities to race. St. Louis has a murder rate even higher than Baltimore’s. It has suffered from similar levels of employer abandonment, worsened by the national corporate mergers that have shuttered or decimated once-thriving local companies.

Pittsburgh, the city that Kahn and McComas label the most resilient of the six, has a crime rate far lower than Baltimore’s — barely a quarter as many murders, according to recent data. It has endured large population losses, but its inner neighborhoods, and now some of its outer ones, have become noticeably trendy.

It also has had stable political leadership, and an exceptionally competent current mayor in Bill Peduto. It boasts top-quality medical centers with worldwide research reputations. Its steel industry is all but gone, but the city has created a thriving new franchise in robotics. It has attracted Google, Uber and Bayer, among other corporations, and has been a magnet for venture capital. It has an impressive roster of civic-minded nonprofit foundations. Are these positive attributes causes or consequences? That’s one of many challenging puzzles that Kahn and McComas can’t really resolve.

TOLSTOY FAMOUSLY WROTE that all happy families are alike but unhappy families are unhappy in different ways. With apologies to Tolstoy, I would argue that cities are exactly the opposite. The successful ones all have a distinct story to tell — great universities, or stable political leadership, or favorable geography, or a series of path-breaking inventions, or something else that is special. Sometimes they have more than one of these.

When it comes to stagnant cities, the problems always seem to be similar: a failure to attract outside corporate investment and venture capital; a weak minority-owned business sector that doesn’t create many jobs; abysmally poor school performance; and a distressingly high rate of child poverty. (Detroit and Cleveland are both over 50 percent.) They all go together, almost all the time.

So what can stagnant cities actually do to revive themselves? Kahn and McComas are honest in admitting they aren’t really sure. “We still do not know the formula for ending poverty,” they write in one of the book’s more prominent understatements. They don’t set out an agenda. What they produce is more like a laundry list.

Some of the items are large in scope: The authors would like struggling cities to lure more immigrants, elect mayors from the private sector who grasp entrepreneurship better than career politicians, and work harder to woo venture capitalists. All easier said than done. Other suggestions are recycled experiments of the past few decades that have met with only spotty success: participatory citizen budgeting and budgeting for outcomes, for example.

Kahn and McComas declare in bold terms that reducing the crime rate is job No. 1 for places like Baltimore and St. Louis. Some of their ideas are practical and seem eminently achievable, given the deployment of sufficient resources: They want to see more detectives working to clear up criminal cases. In 2020, only 32 percent of Baltimore’s violent crimes resulted in an arrest.

Other ideas are fanciful, to say the least. The authors are believers in cognitive behavioral therapy and suggest that it might be provided on a mass basis to poor youngsters in deprived neighborhoods. Without debating the validity of this therapeutic technique, one has to point out that it could never scale up enough to be broadly effective. The resources, financial or professional, couldn’t remotely exist to provide therapy sessions to hundreds of thousands of impoverished kids in the inner cities of Baltimore, Cleveland or Detroit. It’s a flight of imagination.

What the authors believe in more than anything else is innovation. They invoke it so often that it’s not entirely clear what they mean. “The puzzle,” they write at one point, “is why these cities are not experimenting more to better supply needed services.”

But calling for experimentation or innovation doesn’t take us very far toward prescribing what we should actually do. It reminds me of a publisher I once worked for who said: “You know what we really need around here? It’s genius.” Well, yes. Too bad it’s in such short supply.

Innovation and experimentation are good things. But they also tend to be slogans. Confronted with an intractable societal problem, politicians are fond of calling for a Marshall Plan, or a commitment equivalent to the space program of the 1960s. Every time you hear one of those, you should consider them as evidence that the speaker doesn’t really have much of a clue about what to do.

Impassioned pleas for innovation, like demands for a Marshall Plan, are ultimately based on the conviction that if we work hard enough and spend enough money, any social problem is ripe for solution.

I wish that were true.