In the wake of the shooting in Newtown, Conn., the stock prices of two publicly held companies that specialize in gun manufacturing fell sharply. The chart shows that the stocks of Smith & Wesson Holding Companies and Sturm, Ruger & Co. were basically treading water through much of the day, but then fell about 4 percent in the afternoon as details of the horrific episode became apparent.

As was usual in the case of such events, calls for gun control were muted. But the stock market is famously a futures market; investors try to anticipate what might happen to companies in the future. And it’s reasonable for shareholders to think that events such as this might spur measures that would make it more difficult for people to buy guns.