Generations: The Real Differences Between Gen Z, Millennials, Gen X, Boomers, and Silents―and What They Mean for America's Future

Social psychologist Jean M. Twenge, drawing on more than 30 years of research and 24 datasets encompassing 39 million people, argues that generational differences are real, measurable, and driven primarily by technology rather than by major historical events alone. She proposes the "Technology Model of Generations," in which technological progress is the root cause of generational change, operating both directly and through two secondary forces: individualism, meaning a growing cultural emphasis on personal choice, self-expression, and equality, and a slower life trajectory, meaning people take longer to reach milestones of adolescence, adulthood, and old age. These linear forces, Twenge contends, have broken the cyclical patterns of generational types predicted by earlier theorists like William Strauss and Neil Howe, producing six distinct American generations whose behaviors, attitudes, and mental health differ in ways that can be traced through decades of survey data.

Twenge begins with the Silent generation (born 1925–1945), a group situated between the Greatest generation, born before 1925, and the Baby Boomers (born 1946–1964). Despite their name, Silents led the civil rights movement, the feminist movement, and the early LGBT rights movement, with figures like civil rights leader Martin Luther King Jr. and future Supreme Court justice Ruth Bader Ginsburg pushing for equality. They married younger than any other 20th-century generation, with the median age for brides reaching an all-time low of 20.1 in 1956, and had large families during the postwar baby boom. They were the first generation to attend high school and college in large numbers, benefiting from low-cost public education. Survey data shows they hold the lowest rates of mental distress and suicide of any generation born in the first half of the 20th century, likely because they avoided direct combat in World War II and built careers during the postwar economic expansion.

The Boomers, numbering 76 million, formed a demographic bulge that dominated American culture at every life stage. Twenge argues that while the 1960s counterculture was led mostly by Silents, Boomers made its core values of individual choice and self-expression mainstream. Data from the Google Books database shows surges in individualistic words like "unique" and "identity" beginning in the 1960s. Boomers broke the taboo against premarital sex, with the percentage of Americans calling it wrong dropping from 85% in 1967 to 37% in 1979, and had fewer children than Silents, aided by the birth control pill introduced in 1960. They continued the upward trend in divorce and saw unprecedented substance use, with the high school Class of 1979 reporting that 94% had tried alcohol and 62% had tried marijuana. In the area of race, the Voting Rights Act of 1965 dramatically increased Black voter registration and school and neighborhood segregation decreased, yet the income and wealth gaps between Black and White households remained stubbornly unchanged. Women entered professional fields in large numbers, and public attitudes toward gender equality improved steadily. Politically, Boomers shifted from liberal Democrats in the 1970s to majority Republican by the 2010s. Twenge presents extensive evidence that Boomers have worse mental health than Silents, including lower happiness, higher suicide rates, and "deaths of despair" from drug overdoses, suicide, and liver disease, which she attributes to rapid individualism, high divorce rates, and widening income inequality.

Generation X (born 1965–1979), a small generation sandwiched between larger ones, was the first to take individualism for granted from childhood, the last to have an analog childhood, and the first to enter adulthood with the internet. Gen X'ers founded many of the internet's foundational companies, including Google, YouTube, eBay, PayPal, and Twitter. They had an unusual life trajectory: a fast adolescence with earlier sex and more teen pregnancies, combined with a slow adulthood marked by later marriage and delayed careers. Gen X continued trends toward higher self-esteem and materialism begun by late Boomers. Trust in other people, government, and institutions declined sharply with Gen X, a trend Twenge links to rising income inequality. Gen X was the first generation in which more than half supported same-sex marriage and tilts more Republican than any other generation measured since 1952, shaped by coming of age during Ronald Reagan's popular presidency. Gen X'ers have been notably slow to enter leadership positions, holding far fewer governorships, Senate seats, and CEO roles than Boomers did at the same age, largely because the larger Boomer generation has been slow to retire.

Millennials (born 1980–1994) were raised during economic optimism with relentless positive messaging about self-worth, including participation trophies, grade inflation, and self-esteem programs. Survey data shows that Millennial teens scored higher on self-esteem measures and were more likely to believe they were above average, even as standardized test scores remained flat or declined. Twenge challenges the narrative that Millennials have been economically devastated, presenting Census data showing that Millennial households earn more than previous generations did at the same age and that poverty rates are lower. She attributes the persistent perception of economic hardship to high expectations creating disappointment, social media amplifying upward comparison, and negative news coverage. Millennials delayed marriage to historically unprecedented ages and sent birth rates to record lows, driven by the slow-life strategy, individualism, and shifting priorities rather than primarily by economic factors. The generation is the least religious in American history, driven by individualism's incompatibility with collective religious structures. Politically, Millennials lean Democrat and liberal. The "Great Awokening" beginning around 2015, a sharp leftward shift in attitudes on racial discrimination, saw White Democrats become as likely as Black Americans to attribute racial disparities to discrimination. Twenge traces Millennials' mental health from a happy adolescence to a troubled adulthood, with depression rates among 26- to 34-year-olds soaring in the mid-2010s and deaths from drug overdoses and suicide increasing sharply.

Generation Z (born 1995–2012), the most racially diverse generation of American adults, is the first to spend their entire adolescence in the smartphone era. Twenge documents their embrace of gender fluidity, with one out of 18 young adults identifying as transgender or nonbinary in 2021–2022, and surging LGB identification driven almost entirely by increases in bisexual women. Gen Z follows the slow-life trajectory to its fullest expression: As 12th graders, they are less likely to drink alcohol, date, work for pay, get a driver's license, or have sex than any previous generation measured. Twenge presents the book's most alarming data in documenting a comprehensive mental health crisis among teens after 2012: Depression more than doubled, the suicide rate for 10- to 14-year-olds tripled, and the teen suicide rate nearly doubled between 2007 and 2019, all well before the COVID-19 pandemic. She builds a detailed case that smartphones and social media are the primary cause, citing four types of evidence: timing aligned with smartphone adoption; shifts in daily life from in-person to online socializing; group-level effects on social dynamics; and disproportionate impact on girls, who spend more time on social media and are more affected by social comparison. International data from dozens of countries shows the same pattern. Gen Z is markedly pessimistic, with only 36% of 18- to 24-year-olds reporting pride in being American in 2021, and politically polarized from a young age, with both far-left and far-right identification increasing among high school seniors.

Twenge briefly profiles the youngest generation, Polars (born 2013–2029), named for political polarization and melting polar ice caps, noting they will be the first with a non-White majority. While children are physically safer than ever, concerning trends have emerged: The number of young children who are physically inactive doubled between 2012 and 2019, and the number of overweight two- to five-year-olds jumped 26%, likely linked to increased screen time.

The book concludes with projections for the future. Twenge predicts that remote work will remain a permanent fixture, stabilizing at about 31% of paid workdays, that birth rates will continue to decline, and that Millennials and Gen Z will increasingly lean Democrat based on research showing that presidential approval during one's formative years shapes lifelong political affiliations. She argues that regulating social media is among the most important tasks of the 2020s. Technology, she concludes, is both the greatest gift and the greatest challenge facing all six generations: It has produced longer lives, unprecedented freedom, and extraordinary convenience, but has also isolated people, fueled political division, and triggered a mental health crisis among the young.