Wrangling over the 1990 census began in earnest last week, with officials of numerous jurisdictions lining up to take potshots at the preliminary figures, and it's likely to get a lot noisier before it finally quiets down, oh, maybe sometime early in 2000 -- when the forms for that decade's census go into the mail. But no matter how you slice and dice the 1990 figures, one conclusion is inescapable: For the grand old cities of the industrial Northeast and Midwest, the 1990 census is a disaster.

There's no gentler way to put it. From Baltimore to Philadelphia to Chicago to Detroit, population figures are down, down, down, so their legislative representation and tax revenues are headed in the same direction. To be sure, there's plenty of room for argument over the precise details of their population decline; many city officials say the Census Bureau overlooked substantial population blocs, and some of them have been heard to mutter that it's all a Republican plot to shift the balance of political control from the Democratic cities to the Republican suburbs -- as if that shift hadn't already taken place.

But you can quibble the night away, and at daybreak the cold truth is still going to be staring you in the face: Baltimore down 8.5 percent from 1980, Philadelphia down 8.6 percent, Chicago down 9.3 percent, Detroit down a heartbreaking 19.4 percent. The cities that only a quarter-century ago were still the great engines of American industrial and commercial might, and the smaller cities that are their mirror images in miniature, are dying before our eyes -- or, if not exactly dying, changing in ways so radical that their continued existence, not to mention health, is in jeopardy.

What's happening is no mystery: It's the flight of the middle class from urban row houses and apartments to suburban tract developments. It is, as we are now coming to understand, a phenomenon more of class than race. In the District of Columbia, a major drain on the city's tax rolls has been the movement of middle-class blacks into Prince George's County. In Baltimore, where the population decline of 66,000 is 24,000 more than the state's Office of Planning had predicted, Glenn McNatt of the Evening Sun writes: "It will be interesting to compare the outflow of middle-class blacks, in particular, against the previous decade. I suspect this group may make up a surprisingly large chunk of the 'excess' 24,000 people who departed since 1980."

Whatever their race, the people who leave these cities are not, in various important ways, actually leaving them at all. The person who migrates from Washington to Cheverly, or from Baltimore to Reisterstown, takes his chattels and his tax dollars out of the city, but much of the rest of his life stays there: his job, his cultural life, his sources of news and information and entertainment. In any number of jurisdictions in Baltimore County, mail with a Baltimore address reaches its county recipients unerringly; the mailman knows, even if no one else does, that wherever these people may live, they are residents of an area that is defined by, takes its name from, the city at its center.

This is what makes the current census figures so frustrating for people who believe not merely that the old cities deserve to survive but that their health is essential to the well-being of their larger surroundings. The figures show Baltimore declining, indeed declining dramatically, yet in some ways precisely the opposite is true. "Baltimore," this being the metropolitan area fanning out from its downtown core, is growing and prospering as rarely before in its history; combined as it now is with Washington into a single metropolitan statistical unit, it is one of the largest and most influential in the country.

The same is true in varying degrees of all the cities of the Northeast and Midwest save those too small or too dependent on a single failing industry to maintain regional growth. The old center cities, built for the age of trolleys and railroads, are crumbling, sometimes around glittering new tourist attractions such as Harborplace; yet the outlying areas built around the automobile, both bedroom communities and industrial/commercial parks, are thriving. Drive around Philadelphia or New York or Chicago or Cleveland -- your car is the only way you can make the trip -- and you see prosperity everywhere.

Consider that in the very week the preliminary census figures were released, three prominent Baltimore brokers offered instructive testimony about the regional economy. "Baltimore diversified dramatically in the 1980s and it was badly needed," one of them said during a news conference at which all three spoke in similar terms. "We don't have an engine that fuels us all the time like some economies do. So the diversity was almost a miracle, because you wouldn't have dreamed that it would have worked as well as it did." In other words, the old industrial city teamed up with its suburbs to become an economic unit in which health care, banking, information and other up-to-date businesses took a lot of the heat off its declining port and heavy industry.

The cities and the suburbs are all in the same boat, but try telling that to the census takers or the legislators or the suburbanites themselves. The census operates along strict lines; if you're in Baltimore you're a city resident and if you're a mile outside in Towson you're a suburbanite, and that's the way you're going to be counted. What this means is that legislators who redraw political units according to population will move political strength away from the cities, and people in Washington who allocate federal funds according to population will sap them of still further public support.

The power, and thus the money, goes where the people are; one man, one vote is a principle of representative government that's pretty hard to argue with, and since the Supreme Court's decision of 1962 in Baker v. Carr it's been a dominant if not controlling element in American political life at all levels. But reality is often more complicated and elusive than the cold statistics with which the census takers and legislators work. The reality of the old cities is that they are being drained by the very suburbs they created, and that the only way to prevent their collapse into sinkholes of crime and hopelessness and decay is to redraw governmental jurisdictions so that suburbanites reassume the responsibilities they escaped by fleeing the cities upon which they still depend.

Metropolitan government would replace an existing system in which city voters and suburban voters are pitted against each other, at times deliberately and calculatedly so. Their interdependence is clear, yet the system makes them enemies rather than allies; it deprives the city not merely of the tax revenues that suburbanites who work there should be paying, but perhaps even more important, it deprives the city of the increased political clout that metropolitan government would bring.

It's true, as McNatt of the Evening Sun writes, that "the best hope of reversing {Baltimore's} declining fortunes probably lies in a dramatic turnaround in its public schools." People flee to the suburbs in search of better schools, and those who stay behind are ill-served by the schools they attend. But any city official anywhere will tell you that you can't improve schools without money; money is what all old cities need, and money is what the existing structure systematically denies them. Without metropolitan government, all other remedies are mere Band-Aids.