If there really is a proverbial shelf on which countless state reports gather dust, legislators should visit it and pull down one from 1984 with the unpromising title of “Maine State Bond Policy.” Not only is it an excellent primer on the state’s indebtedness, the report accurately predicts conditions that exist now and — like the Ghost of Christmas Future — says what will happen if Maine doesn’t change its ways.

The report, by Stanley Provus, a former acting director of the Maine State Housing Authority, suggests ways of using Maine’s debt more effectively. It takes special pains to point out that the way Maine sets its debt limit is one of the most self-destructive processes in government.

Since the 1970s, new debt for any year generally has been limited to 90 percent of the debt Maine retired in the previous year. Known as the 90 percent rule, it was established when bonding houses expressed their displeasure over the amount Maine was borrowing. With its credit rating in jeopardy, Maine started to cut back. By the time of the ’84 report, the state had cleaned up its debt problem, but remained committed to the limit and has more or less stuck to the guideline ever since. Maine easily has the lowest level of debt in New England and is well below the national average. That’s an enviable position to be in, but the eventual effect of the 90 percent rule is easy to predict: Maine will not be able to borrow a nickel.

Before saying, “Sounds about right,” consider what would happen if, as a first-time home-buyer, you couldn’t borrow money for a mortgage. What kind of home would you get, if you could get one? How about the car loan so that you can travel to a new job? No loan, no car, no job. How about the college loan to advance your career? Just as it can make sense for individuals to take on debt, it can make sense for the state.

Here’s where the ’84 report is prescient:

“If used in the future,” it says, “a 90 percent yardstick would fail because it assumes the state will need increasingly less rather than more capital investment over the next two decades. Such a policy could easily give rise to extraordinary maintenance expenditures and the necessity for extraordinary captial investments at a future date when capital investments become unavoidable.”

Turns out the future — ta da! — is now, and it’s going to cost Maine plenty.

Schools are falling apart, and the estimated cost to put them back together is $525 million. Plans for a long-overdue prison overhaul came in with a price tag of $165 million. The Department of Transportation has a list as long as the state of roads and bridges that need replacement — $794 million worth over the next decade. Even the State House needs serious repair. Water projects, children’s services, mental-health infrastructure — the nuts and bolts of government — all have strong cases for renewed investment. Maine has deferred maintenance for a generation, and now the bill for this penny-wise approach has come due.

Only Maine can’t borrow to pay it.

Change the system

Actually, it can borrow for it. The 90 percent rule is not carved in stone or even printed in statute. It is merely a habit, impressed on the minds of some lawmakers who think that the public always wants less money spent and would not understand why going into debt for some projects is worthwhile. When they propose bonds beyond the 90 percent guideline, as they did this session, they do so quietly — more quietly, in fact, than they need to. The regular success of environmental and road bonds in the November elections suggests voters are well aware that paying to maintain is a lot cheaper than paying to replace infrastructure.

But even if voters supported all worthwhile bond questions, the 90 percent rule inevitably pushes Maine further behind in its repairs. The state needs a new way of setting its level of debt. State Treasurer Dale McCormick recently suggested what Mr. Provus suggested 14 years ago: Tie the debt ceiling to revenues, which amount to the ability to pay off loans. Both have suggested a ceiling of 7 percent of revenues, with the state able to increase that to 8 percent in the event of an emergency.

It’s not clear that 7 percent is the ideal number (the current debt level is around 3 percent), but basing debt on revenues makes a lot more sense than basing it on a condition that has not existed since the Carter administration. Gov. Angus King, who is also reviewing the 90 percent rule, is considering a plan that would tie the debt limit to the level of per capita income. Because income does not swing as dramatically as state revenues as the economy rises and falls, the per-capita link has the advantage of producing more dependable debt ceilings.

There are good arguments for either of these approaches and no doubt are other ways to stay to a level of debt that both allows Maine to support its schools, roads and prisons and is affordable in good times and bad. The first step is to agree that the 90 percent rule has outlived its usefulness. The second step is for state leaders to start offering arguments for a better ideas for a new way of looking at debt, one grounded in financial sense.