NO MATTER how one measures the effectiveness of a law, the District's anti-speculation tax seems a failure. City officials told the D.C. council last week that they have taken in less than $10,000 under the 3-year-old tax, while administering the tax has cost the city over $66,000. The city's Department of Finance and Revenue issued a report that attempts to answer the related question of whether the tax has stopped speculation. It found that 70 percent of the property owners who acted as speculators, under the definition of the law, ognored the tax. The report added that there are legal ways for speculators to circumvent the tax even if they choose not to flout it.

In the face of this evidence, the council voted last week to extend the anti-speculation tax as emergency legislation for 90 days. Its rationale was that the law exists as a deterrent to speculation and not a way to raise money. It may be, some council members argue, that the speculators are scared away by the law and that is why the tax raises little money. And if it is true that 70 percent of the people who should pay the tax are avoiding it, says council member David Clarke (Ward 1), then there are problems with the enforcement of the tax -- not with the tax itself.

Are the people charged with enforcing the law doing a bad job? Or is the law to difficult to enforce? The question is answered by officials of the Finance and Revenue Department, who say that there are so many exceptions and loopholes in the law tht any true speculator need not stop speculating to avoid paying the tax. The enforcement problem, in other words, is not so much a result of negligence by city workers as it is a reflection of the fact that the law was badly drafted.

If the city council wants a speculation tax, it should first make the law tighter. As it stands, the law is an expensive ornament to the city's law books, having already cost the city several thousand dollars to enforce with no apparent results. But tightening the law to allow better enforcement is really a secondary matter. The main question is whether the city needs the tax at all. The council has failed to make the case that it does. Council members have only pointed angrily at the specter of evil speculators without offering any proof that there is a large problem that requires the remedy of a punitive tax.