The property tax is regressive, unfair … and unavoidable.

January is tax time in Boston, and this January's bills have brought bad news to many who are finding themselves subject to sharp tax increases.

The tax is unfair for two related reasons. The first is that it is a tax on wealth, not income. The tax is imposed upon a property's assessed value. If the value goes up, the amount of tax goes up — and it doesn't matter whether the owner's income has gone up, down or stayed the same.

Particularly vulnerable are those on fixed incomes, such as the elderly, who draw little comfort from the notion that their property is increasing in value. Their incomes are not, and they suddenly find themselves in the sorry position of having to sell their property and move in order to pay their taxes. They would rather, of course, just stay put.

The second source of unfairness relates to Proposition 2½. As most homeowners know, Proposition 2 ½ limits annual tax increases to 2.5%. That limit applies citywide, however, and not to an individual or a neighborhood. Thus, if one neighborhood's property values go up and another goes down, the homeowners in the first neighborhood will find themselves paying dramatically higher taxes. Those in the second will pay dramatically less.

It will probably not surprise readers of this newspaper to learn that Beacon Hill and Back Bay typically see sharp increases in their taxes. This happens despite the fact that an enormous number of those neighborhoods' residents are older and on fixed incomes.

So what is to be done? In truth, not much.

The best solution would be to identify some other source of revenue for the city. Taxes based upon income or sales are usually fairer and (because they are less subject to the vagaries of the real estate market) more stable. But creating a city income tax or adding a surcharge on top of the sales tax may create far worse problems. Unlike real estate, workers and shoppers are mobile. Other cities around America have learned with much regret that boosting these types of taxes just causes people to go to towns where the taxes are lower. (Want proof? Ask Massachusetts liquor stores located near the New Hampshire border.)

Still, we should watch carefully the city's upcoming experiment with new surcharges on hotels and rental cars (which will be used to fund the new convention center). Carefully done, it may be possible to devise another tax system that could partially replace the property tax and not put the city or its residents at an economic disadvantage.

Some other, more targeted, palliatives are possible. One thought is to create special rules for the elderly or those on fixed incomes. For example, we may want to allow those particularly hurt by tax increases to in effect "bank" their new taxes by putting a lien on their property. The bill would become due only when the property is sold or probated.

But fixes like this only delay the tax. They don't make it any more fair.

There is one other possibility. For the last twenty years, Boston's tax rate has been, literally, as high as it's legally allowed under Proposition 2½. In the next few years the city will see a surge in revenue as a result of major new construction projects that are presently in the works. The response of most politicians is to dream up new ways to spend that money.

There is an alternative. Instead of spending it, perhaps we could give it back to Boston's residents in the form of a tax cut. Now that would make opening the tax bill next January just a little less painful.