AFTER POINTING OUT such state budget trivia as the fact that poor people and immigrants can hardly be the cause of our fiscal woes, I am often asked, “Well, where does the money go?”

Like most interesting questions, this has a complicated answer, but it has an answer. I don’t have my finger on all the parts of it, but I see some of it, and a big part is something very few people pay attention to, perhaps on purpose.

It’s said that fish don’t notice the water, and like those clueless fish, most of us don’t give the shape of our world much thought. It’s just how the world is, after all. Providence is a city, where some people work and lots of poor people reside. Some rich people live there, too. The suburbs are less expensive to live in, and have better schools. Some suburbs are quite rich towns, and so on. These things have been true for a long time.

But they haven’t been true forever. Browsing in Rhode Island Department of Education archives, I recently ran across a report listing the property value per student in each of Rhode Island’s towns in 1950, and it’s a pretty different list than you’d make today.

Narragansett is at the top of the list, because of a few grand mansions and because it only had about 400 students. But the top of the list is actually dominated by the state’s cities. After Narragansett came Providence, Pawtucket, Woonsocket and Central Falls right in a row. (The complete list was published in last month’s Rhode Island Policy Reporter.) This is pretty easy to understand.

In 1950, the city was where the action was. The country was for rubes. Providence’s schools were the pride of the state, and the taxes were lowest there, too. Hopkinton had the highest tax rate of any city or town.

Needless to say, this isn’t the case any more.

Similar surprises were further down the 1950 list. East Greenwich was near the basement, just a bit above Warwick and a few notches behind North Kingstown.

What happened? Well, people moved out of the cities, and we had a baby boom. But you may not have noticed, because you grew up in the world where both of these things were so easy to take for granted.

As people moved from the cities, they were selling land and houses there, driving down prices, and buying land out of town, driving up those prices. Results were that through the 1950s and ’60s, not only were suburban population growth rates of 4 percent and 5 percent a year not at all uncommon (in North Kingstown, Coventry, East Greenwich, among others), but the prices of property went up fast, too. When tax rolls grow that fast, and land values are increasing, revenues grow, too. Under those conditions, anyone can balance a budget, and many did so while clucking sanctimoniously at the cities. (Many still do.)

Meanwhile, in the cities, inflation-adjusted property values declined, but services couldn’t. Providence has only two-thirds the number of people it had in 1950, and a much smaller fraction of the property value, but it has the same number of blocks to police, about the same number of houses to burn, and more students in its schools.

The growth of suburban budgets financed a 50-year building spree, as we put roads, bridges, schools and fire stations all over the state.

In 1958, we had about 3,020 miles of local roads in the state, according to a report archived in the State House library. In 2006, federal highway statistics show we had 5,538 miles. (We count such miles differently now, so the difference is likely even greater than it seems.) We’ve built sewer systems in Warwick, expanded water systems in Kent County and the East Bay, and converted volunteer fire departments to professional ones all over the state. In essence, we’ve built ourselves almost a whole second state’s worth of infrastructure.

The ironic thing about all this is it’s much more expensive to provide the same level of any municipal service in the suburbs than in the cities. When houses are far apart, it takes more pipe to get water to them or sewage from them. Student transportation costs more, and there are many fewer taxpayers per mile of local roads. So long as any individual town’s growth rate was high enough, this wasn’t a problem, but as soon as growth flags, the piper comes for his due, and years of heedless building have to be paid for.

The other big problem comes when suburban residents start demanding (and/or needing) the same level of services as the cities provide. When people move to the sticks and then demand fire response times comparable to what they’d have in Providence, you have a recipe for very high costs. When crime rates creeping upward make suburban residents demand policing like they’d get in Pawtucket, that’s a problem.

When increasing density increases water pollution to the point that people demand new sewers, well that’s pretty expensive, too.

There is a “blue-ribbon” tax commission meeting through this fall to talk about how tax policy should be shaped for our state’s future.

Let them not fail to take into account the paradox of our tax system: The places where services are expensive are the places with the low taxes.

Think that’s not your problem? You’re in the suburbs and all’s fine with you? Let the cities deal with their own problems? Wait until high gasolines prices start driving people back into the cities, and the shoe will be on the other foot. In the meantime, let’s come up with a tax system that doesn’t penalize us when people move.

Tom Sgouros is editor of Rhode Island Policy Reporter (Whatcheer.net).