As is often the case with a large war, the elation of victory and large numbers of returning males to their country triggered a baby boom after the end of World War II in many countries around the globe, notably those of Europe, Asia, North America and Australasia.

In the United States, demographers have put the generation's birth years at 1946 to 1964, despite the fact that the US birth rate (per 1,000 population) actually began to decline after 1957. William Strauss and Neil Howe, in their book Generations include those conceived by soldiers on leave during the war, putting the generation's birth years at 1943 to 1960. (Strauss and Howe base their years on peer personality, not parental fecundity, so their years may not coincide with the actual 'boom'.)

Interestingly, the birth rate actually began to climb in 1940: From that year through 1943, the US birth rate rose four years in a row for the first time since at least the beginning of the 19th Century; following a brief interruption due to the wartime absence of would-be fathers, the 'boom' picked up where it left off after World War II ended.

In Canada, the baby boom is usually defined as the generation born from 1947 to 1966 – Canadian servicemen were repatriated later than American servicemen, and Canada's birth rate did not start to rise till 1947, and most Canadian demographers prefer to use the later date of 1966 as the boom's end in that country.

The United Kingdom experienced a second baby boom during the 1960s, with a peak in births in 1964.

Whatever year they were born, boomers were coming of age at the same time across the world, so that Britain was undergoing Beatlemania while people in the United States were driving over to Woodstock, organizing against the Vietnam War, or fighting and dying in the same war, Boomers in Italy were dressing in mod clothes and "buying the world a Coke", boomers in India were seeking new philosophical discoveries, American boomers in Canada had just found a new home after escaping the draft south of the border, Canadian Boomers were organizing support for Pierre Trudeau, and boomers in Mexico were discovering new hallucinogenic drugs and rediscovering old ones. Although the term "boomer" has fallen into global use, the generation is also known in Europe as the Generation of 1968.

The term is derived from a historically significant rise in the birth rate following the Second World War. Several factors have been credited with this rise, among them a general sense of relief at the war's end, and the resurgent economic conditions of the period.

See also

• demographics
• demography