Tobacco smoking remains the leading cause of preventable disease and death in Canada.

For the past 25 years, May 31 has been World No Tobacco Day, as declared by the World Health Organization (WHO), with a different theme from year to year. This year's theme is a ban on tobacco advertising, promotion and sponsorship.

To mark the day, we've pulled together some numbers on tobacco use and its consequences in Canada and around the world.

Smoking rates

Among Canadian provinces, smoking rates vary from a low of 15.8 per cent in B.C. to 23.8 per cent in Saskatchewan, according to Statistics Canada's Canadian Community Health Survey for 2011. As the map above shows, the numbers for Canada's North are significantly higher.

Smoking rates have been falling for the last quarter-century, but since 2009 the rate of decline has levelled off. In 2011, 5.8 million Canadians 12 years and older smoked, a rate of 19.9 per cent.

Worldwide, there are about 1.1 billion smokers, about 22 per cent of the adult population. About 80 per cent live in low- or middle-income countries.

Our graph showing the total percentage of smokers in Canada by year goes back to 2003, when the rate was 23 per cent, but smoking rates have declined considerably from nearly a half-century ago. In 1966, 41 per cent of Canadians 15 years and older were smoking.

Significantly more men than women smoke in all age groups, 22.3 per cent compared to 17.5 per cent. However, in the youngest age group, the male and female rates are almost the same.

According to U.S. data, about 80 per cent of high school students who smoke will smoke into adulthood.

The smoking rate in Canada is highest in the 20-24 year age group, for both men and women.

Worldwide, the number of male smokers is about four times the number of female smokers.

The tobacco market

Total cigarette sales in Canada numbered 31.1 billion in 2011. That's down from the 31.7 billion cigarettes sold the year before but higher that the 30.2 billion sold in 2006.

Unlike Canada, worldwide cigarette consumption has been increasing. "Smokers consumed nearly 5.9 trillion cigarettes in 2009, representing a 13 per cent increase in cigarette consumption in the past decade," according to the Tobacco Atlas, by the World Lung Foundation .

In Canada, three manufacturers control 99.5 per cent of the Canadian tobacco market:

Imperial Tobacco Canada Ltd. (51.2 per cent market share). Rothmans, Benson & Hedges (33.5 per cent). JTI-Macdonald (14.8 per cent).

The big three are all owned by multinational corporations. And those three multinationals are highly profitable. For example, British American Tobacco, which owns Imperial Tobacco, had profits totalling $8.3 billion US in 2012.

Canada's three tobacco giants are currently defending themselves in a $27-billion class-action lawsuit in Montreal.

The manufacturers have more than one brand, of course. The top ten brands accounted for 86 per cent of cigarette sales in Canada in 2011. The three top-selling brands are manufactured by Imperial Tobacco:

Du Maurier (19.3 per cent market share). Player's (16.7 per cent). Peter Jackson (11.7 per cent).

Smoking and health

According to a 2007 study by the Centre for Addiction and Mental Health in Toronto, smoking is responsible for 16.6 per cent of all deaths in Canada.

The study, based on 2002 data, found that 21 per cent of deaths in men and 12.2 per cent of deaths in women were attributable to smoking.

The authors estimate that the smoking-attributable deaths that year resulted in Canadian residents losing a total of 515,608 years of life.

They report that for the 37,209 deaths they attribute to smoking:

46 per cent were due to cancer.

27.6 per cent to cardiovascular disease.

22.3 per cent due to respiratory diseases.

Tobacco is responsible for killing one in 10 adults worldwide, according to the WHO.

The organization claims that tobacco caused about 100 million deaths in the 20th century. Based on current trends, they estimate that tobacco "may cause about one billion deaths in the 21st century."

WHO estimates that second-hand smoke causes 600,000 premature deaths per year, with children accounting for 28 per cent of those deaths.

U.S. data shows an estimated 50,000 deaths per year as attributable to second-hand smoke, mostly from heart-disease.

In Canada, according to the 2011 StatsCan survey, 15.1 per cent of Canadians 12 years and older were exposed to second-hand smoke at home.

WHO estimates that comprehensive national smoke-free laws protect just 11 per cent of the world's population but "the number of people protected from second-hand smoke more than doubled to 739 million in 2010 from 354 million in 2008."

A 2004 report by the U.S. Surgeon General estimates that for every death attributable to tobacco, 20 people are living with a tobacco-caused disease.

Tobacco control

WHO has also looked at the effectiveness of various methods of tobacco control. It claims that:

"A comprehensive ban on all tobacco advertising, promotion and sponsorship could decrease tobacco consumption by an average of about seven per cent ."

." Increasing tobacco prices by 10 per cent through tax hikes, "decreases tobacco consumption by about four per cent in high-income countries and by up to eight per cent in low- and middle-income countries."

WHO says that their Framework Convention on Tobacco Control, which has been in force since 2005, is "one of the most widely embraced treaties in the history of the United Nations." Canada is a signatory.

Quitting smoking

In 2010, over 60 per cent of Canadians who had been smokers had quit.

One year after someone quits smoking, the risk of coronary heart disease falls by half.

About 10 years after someone quits, the risk of dying from lung cancer falls by half.

The major sources for this story are Statistics Canada's Canadian Community Health Survey, a study from the Centre for Addiction and Mental Health, The World Health Organization and The Tobacco Atlas from the World Lung Foundation and the American Cancer Society. See the external links in the left column in some browsers.