CRIME RATES are down almost everywhere in the country. But Attorney General William French Smith, in hailing these FBI Crime Index figures, sensibly refrained from claiming any great credit for the trend. Apparently he and FBI Director William Webster understand that most Americans think there is not much the federal government can do, one way or the other, to affect crime rates. On this issue this administration, unlike some of its predecessors, has been careful not to promise what it can't deliver.

Crime rates, as the FBI acknowledges, are some of our most slippery statistics. Nevertheless, the trend toward lower crime rates across the nation in 1982 is extensive and uniform enough that it almost certainly signifies some real change. It is a change that you could have predicted 20 years ago if you had paid attention to birthrates. Most crimes are committed by men between ages 15 and 25. The birthrate in this country declined sharply beginning in 1962. From those two facts anyone could have deduced--and some, like Sen. Daniel Patrick Moynihan, did--that crime rates would drop sometime in the early 1980s.

It's important to note that crime did not rise in a time of high unemployment. Joblessness was up in 1982, but crime was down. The one part of the country where crime rates rose significantly was in the oil states of Texas and Oklahoma, which during most of the year had some of the nation's lowest unemployment rates. The rise in the number of crimes there may simply reflect population growth. Certainly there's no warrant for saying that people are driven to crime by economic necessity. We should reduce unemployment, but not because it leads to crime.

Trends in crime rates may be predictable, but each crime is committed by a specific person who should be held responsible for his conduct. There are many things that local officials, police departments, ordinary citizens and perhaps even federal officials can do to reduce further the number of crimes. Director Webster struck the proper note when he cited such efforts and said that "perhaps those efforts are finally having an impact on the crime problem." Whatever comfort we may take from these crime statistics, for any victim one crime is one too many.