In a general sense, a baby boom is any sudden, substantial and sustained increase in the birthrate. The term baby boomers is commonly used to refer to Americans born post-WWII, between the years of 1945 and 1964, approximately 76 million in number. They are sometimes referred to as the baby boom generation, although someone born in 1945 could easily have given birth to someone of the next generation by 1964.
Persons born in the first half of the time span, approximately 1945-1955, are sometimes known as early boomers. Those born after 1955 are sometimes called late boomers. Many observers have noted that the baby boom generation is far from monolithic. Indeed there are significant differences between the early boomers and the late boomers, especially those late boomers born in the 1960s.
The first baby boomers turned 65 in 2011, giving rise to concerns about what will happen when the bulk of the population swell becomes eligible for Social Security and Medicare. The number of people 65 and older is expected to double between 2010 and 2050.