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However, these comparisons often overlook one important difference between the generations — their memberships are not defined by the same metric. That is, while birth cohorts included in the baby boomer generation are associated with a rise in fertility, no similar demographic event can be used to distinguish the birth cohorts included in the millennial generation. Notably, shared experiences rather than demographics define the millennials.

Over the next several years, baby boomers will continue transitioning into retirement and old age while millennials, many of whom are children of the baby boomers, pass through the traditional benchmarks of adulthood (e.g., finishing school, finding jobs and buying homes). Researchers and reporters, among others, have drawn comparisons between the experiences and behaviors of these two generations.

Because of this, the birth years for this generation are not as distinguishable as those of the baby boomers. The Census Bureau does not provide guidance on which years are included in the millennial generation, and many definitions are used by the public. For the purposes of this blog, I use the term “millennials” to encompass those born between 1982 and 2000.

Figure 1 shows births for the years 1909 through 2013. A large increase in the number of births between 1945 and 1946 marks the start of the baby boom generation, but there is no corresponding increase to establish the start of the millennial generation.

Although the birth cohorts comprising the millennial generation were as large, and in some cases larger, than those of the baby boomer generation, the millennial generation differs from the baby boomers because these large birth cohorts are part of a broader trend that started in the previous generation and is continuing into the next.  In other words, the fertility trends associated with the beginning of the millennial generation are not exceptional.

One consequence of this difference relates to the impact that these generations have on societal institutions. Despite the similar size of the millennial generation relative to the baby boomers, their transition through life thus far has not introduced the same level of shock as the baby boomers caused.

To illustrate this point, I use the example of school enrollment for 5 and 6 year olds. Figure 2 shows the annual change in the number of 5 and 6 year olds enrolled in school. For the majority of years, the number of students remained relatively stable. One exception was the 1.4 million increase in students between 1953 and 1954. The growth in 1954 corresponds to children born between 1947 and 1949 (the first of the baby boomers) enrolling in school. This increase is nearly triple that experienced at any point during the millennial generation’s transition into school and represents an increasing demand on the education system not replicated by the millennials.

The goal here is not to minimize the millennial generation’s significance, only to highlight important differences in the origin of this generation and its impact on societal institutions as its members transition through the course of life.