GMAT Critical Reasoning (CR) | Re: In the United States in 1986, the average rate of violent

In the United States in 1986, the average rate of violent crime in states with strict gun-control laws was 645 crimes per 100,000 persons—about 50 percent higher than the average rate in the eleven states where strict gun-control laws have never been passed. Thus one way to reduce violent crime is to repeal strict gun control laws.
Which of the following, if true, would most weaken the argument above?

(A) The annual rate of violent crime in states with strict gun-control laws has decreased