"This is potentially devastating from a health standpoint," said David Sweanor, a Canadian attorney who has studied how smokers respond to fluctuations in cigarette prices. "Affordability is far and away the most important element in tobacco consumption, more so than any other factor," such as public-health campaigns, warning labels or restrictive advertising regulations.

Sweanor said per-capita cigarette consumption in the United States and Canada was roughly equal in the early 1980s, but that Canadian smokers have quit at a faster rate since then as cigarettes became relatively more expensive, mostly because of sharply higher cigarette taxes.

The price of a pack in Canada has risen more than 165 percent to $5.54 since 1981, while consumption has fallen 50 percent, Sweanor said. In the United States, where the average pack cost $1.84 last year and prices have increased 72 percent since 1981, per-capita consumption has fallen just 28 percent. A similar inverse relationship between consumption and price has been found in studies of smoking in Britain, he said.