At any given moment in time, age group differences can be the result of three overlapping processes, says the report.
- Life cycle effects. Young people may be different from older people today, but they may become more like once they themselves age
- Period effects. Major events affect all age groups simultaneously, but the degree of impact may differ according to where people are located in the life cycle
- Cohort effects. Period events and trends often leave a particularly deep impression on young adults that stay with them as they move through their life cycle
Generational names are the handiwork of popular culture, says the report. Some are drawn from a historic event; others from rapid social or demographic change; others from a big turn in the calendar:
- The Millennial generation falls into the third category. The label refers those born after 1980, the first generation to come of age in the new millennium.
- Generation X covers people born from 1965 through 1980. The label long ago overtook the first name affixed to this generation: the Baby Bust. Xers are often depicted as savvy, entrepreneurial loners.
- The Baby Boomer label is drawn from the great spike in fertility that began in 1946, right after the end of World War II, and ended almost as abruptly in 1964, around the time the birth control pill went on the market. It's a classic example of a demography-driven name.
- The Silent generation describes adults born from 1928 through 1945. Children of the Great Depression and World War II, their "Silent" label refers to their conformist and civic instincts. It also makes for a nice contrast with the noisy ways of the anti-establishment Boomers.
- The Greatest Generation (those born before 1928) "saved the world" when it was young, in the memorable phrase of Ronald Reagan. It's the generation that fought and won World War II.