To the Editor:

Your Economic Watch article on the high hidden costs of the war on marijuana (Sept. 5) is informative, but like much reporting on the topic, lacks historical perspective. This is most prominent in the discussion of legalization.

''Legal marijuana,'' it is stated, ''could be a major source of tax revenue rather than a $14 billion business for criminals and a billion-dollar cost to the Treasury. But there is little support for such a radical experiment; it is generally agreed that more people would smoke marijuana if it were legal, just as more people began drinking alcohol with the end of Prohibition in 1933.''

This paragraph perpetuates the popular misconception that marijuana has been illegal since the beginning of time. Of course, it has not, nor has any drug; indeed, it is the prohibition of marijuana that is, as the prohibition of alcohol was before repeal, an experiment - and to judge from ''Marijuana: Costs of Abuse, Costs of Control,'' the Michael Kleiman report that occasioned your article, and from the collective experience of those charged with enforcing this prohibition, a failed experiment. The same can be said for the criminalization of all recreational drugs.

Also, this paragraph ignores that in recent years, with the public recognition of the health hazards inherent in the consumption of alcohol, and resulting from better public education about these hazards, per capita consumption of all alcohol has declined significantly, with a steeper decline in the category of distilled spirits, which have the highest concentration of alcohol and carry the highest risk. This, despite the constant advertising of these spirits on billboards, in public transportation and in every edition of The New York Times Magazine, among other places.