The following editorial appeared Monday in the Washington Post.

The numbers are dramatic – and encouraging. Americans smoked fewer cigarettes last year than any time since 1951, when the population was half what it is today. Cigarette sales dropped 4.2 percent in 2005 alone and 20 percent since 1998, according to data based on cigarette sales tax figures and compiled by the National Association of Attorneys General.

The state attorneys general have an interest in proclaiming progress in the war on smoking – they attribute much of the decline to the effects of the $246 billion settlement the states reached with the tobacco industry in 1998 – and it’s possible that the study didn’t capture some cigarette sales, such as those conducted over the Internet or through the black market. But the group’s optimistic findings are reinforced by other studies concluding that fewer Americans are smoking and those who do are smoking less.

The Centers for Disease Control and Prevention reported in November that the smoking rate among adults has been falling steadily, from 25 percent in 1993 to 20.9 percent in 2004.

Equally cheering, the proportion of heavy smokers (those smoking 25 or more cigarettes a day) dropped from 19.1 percent of smokers in 1993 to 12.1 percent in 2004. After rising during the 1990s, smoking among high school students dropped from 36.4 percent in 1997 to 21.9 percent in 2003.

No one can pinpoint the precise reasons for the decline – whether anti-smoking campaigns funded by the tobacco settlement, marketing restrictions designed to reduce smoking’s appeal to children or other developments.

A lot of it probably has to do with the welcome fact that smoking has become an expensive hassle. Cigarette prices are up, from an average of $1.74 a pack in 1997 to $3.16 in 2004, in part because tobacco companies passed the cost of the settlement on to consumers.

Taxes are up, too: According to the Campaign for Tobacco-Free Kids, the average state cigarette tax has increased since the settlement from 40 cents a pack to 92 cents.

And for those willing to pay the price, it’s become harder to find a place to smoke: Twelve states and the District of Columbia, along with hundreds of cities and counties, have moved to ban smoking in public buildings, including restaurants and bars.

Unfortunately, Maryland and Virginia have chosen not to join this trend. Legislative panels in both states killed measures last month that would have prohibited smoking in virtually all public places.

But here’s the really bad news. Tobacco is still the leading preventable cause of death, killing more than 400,000 people annually. The Campaign for Tobacco-Free Kids warns that the decline in smoking among young people has slowed, and it criticizes states for not using more of the settlement money to fund anti-smoking efforts.

Americans still smoke an astonishing 378 billion cigarettes annually. That’s 378 billion too many.