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At its core, demography is the act of counting people. But it's also important to study the forces that are driving population change, and measure how these changes have an impact on people's lives. For example, how does immigration affect U.S. population growth? Do Americans feel that children are better off with a parent at home, in an era when most women work? How is the rise of the young-adult Millennial generation contributing to the rise of Americans with no stated religion? For this year's Population Association of America (PAA) annual meeting, here is a roundup of some of Pew Research Center's recent demography-related findings that tell us how America and the world are changing.

1 Americans are more racially and ethnically diverse than in the past, and the U.S. is projected to be even more diverse in the coming decades. By 2055, the U.S. will not have a single racial or ethnic majority. Much of this change has been (and will be) driven by immigration. Nearly 59 million immigrants have arrived in the U.S. in the past 50 years, mostly from Latin America and Asia. Today, a near-record 14% of the country's population is foreign born compared with just 5% in 1965. Over the next five decades, the majority of U.S. population growth is projected to be linked to new Asian and Hispanic immigration. American attitudes about immigration and diversity are supportive of these changes for the most part. More Americans say immigrants strengthen the country than say they burden it, and most say the U.S.'s increasing ethnic diversity makes it a better place to live.

2 U.S. ImmigrantsAsia has replaced Latin America (including Mexico) as the biggest source of new immigrants to the U.S. In a reversal of one of the largest mass migrations in modern history, net migration flows from Mexico to the U.S. turned negative between 2009 and 2014, as more Mexicans went home than arrived in the U.S. And after rising steadily since 1990, the unauthorized immigrant population has leveled off in recent years, falling to 11.3 million in 2014 from a high of 12.2 million in 2007. Meanwhile, Asians are now the only major racial or ethnic group whose numbers are rising mainly because of immigration. And while African immigrants make up a small share of the U.S. immigrant population, their numbers are also growing steadily – roughly doubling every decade since 1970.

3 America's demographic changes are shifting the electorate – and American politics. The 2016 electorate will be the most diverse in U.S. history due to strong growth among Hispanic eligible voters, particularly U.S.-born youth. There are also wide gaps opening up between the generations on many social and political issues. Young adult Millennials are much more likely than their elders to hold liberal views on many political and social issues, though they are also less likely to identify with either political party: 50% call themselves political independents.

4 Millennials, young adults born from 1981 to 1996, are the new generation to watch. By 2019 they will surpass Baby Boomers (born 1946-1964) as the largest U.S. adult generation, and they differ significantly from their elders in many ways. They are the most racially diverse adult generation in American history: 43% of Millennials are nonwhite, the highest share of any generation. And while they are on track to be the most educated generation to date, this achievement has come at a cost: Many Millennials are struggling with student debt. In addition to the weak labor market of recent years, student debt is perhaps one reason why many are still living at home. Despite these troubles, Millennials are the most upbeat about their financial future: More than eight-in-ten say they either currently have enough money to lead the lives they want or expect to in the future.

Note: Item No. 4 in this post was updated on March 23, 2018, to reflect the Center's revised definition of the Millennial generation and the updated year in which Millennials will be the largest generation.

5 Women's role in the labor force and leadership positions has grown dramatically. The labor force participation rate for American women has risen steadily since the 1960s. In fact, mothers were the sole or primary breadwinner in a record 40% of all households with children in 2011. The gender pay gap has narrowed over this period of time, especially for young women just entering the labor force, but it still persists. As more women have entered the workforce, the share of women in top leadership jobs has risen, but they still make up a small share of the nation's political and business leaders relative to men. Why the continued disparity? While Americans say women are every bit as capable of being good leaders as men, four-in-ten believe they are held to higher standards than men and that the U.S. is just not ready to put more women in top leadership positions.

6 The American family is changing. After decades of declining marriage rates, the share of American adults who have never been married is at an historic high. Two-parent households are on the decline in the U.S., while divorce, remarriage and cohabitation are on the rise. About one-in-six American kids now live in a blended family. And the roles of mothers and fathers are converging, due in part to the rise of breadwinner moms. Dads are doing more housework and child care, while moms are doing more paid work outside the home. Americans are conflicted about some aspects of this change: While nearly half of two-parent households have a mom and dad who both work full time, 51% of Americans say children are better off with a mother at home.

7The share of Americans who live in middle class households is shrinking. The share of U.S. adults living in middle-income households fell to 50% in 2015, after more than four decades in which those households served as the nation's economic majority. And the financial gaps between middle- and upper-income Americans have widened, with upper-income households holding 49% of U.S. aggregate household income (up from 29% in 1970) and seven times as much wealth as middle-income households (up from three times as much in 1983). Most Americans say the government doesn't do enough to help the middle class, and neither political party is widely viewed as a champion for middle-class interests.

Middle-income households in U.S.

8Christians are declining as a share of the U.S. population, and the number of U.S. adults who do not identify with any organized religion has grown. While the U.S. remains home to more Christians than any other country, the percentage of Americans identifying as Christian dropped from 78% in 2007 to 71% in 2014. By contrast, the religiously unaffiliated have surged seven percentage points in that time span to make up 23% of U.S. adults last year. This trend has been driven in large part by Millennials, 35% of whom are religious "nones." The rise of the "nones" is not a story unique to the U.S.: The unaffiliated are now the second-largest religious group in 48% of the world's nations. Americans are well aware of this shift: 72% say religion's influence on public life is waning, and most who say this see it as a bad thing.

9The world's religious makeup will look a lot different by 2050: Over the next four decades, Christians will remain the largest religious group, but Islam will grow faster than any other major religion, mostly because Muslims are younger and have more children than any other religious group globally. By 2050, the number of Muslims will nearly equal the number of Christians. In the U.S., the Muslim population will remain small, but is projected to grow rapidly.

10The world is aging. The demographic future for the U.S. and the world looks very different than the recent past. Growth from 1950 to 2010 was rapid — the global population nearly tripled, and the U.S. population doubled. However, population growth from 2010 to 2050 is projected to be significantly slower and is expected to tilt strongly to the oldest age groups, both globally and in the U.S. Public opinion on whether the growing number of older people is a problem varies dramatically around the world. Concern is highest in East Asia where large majorities describe aging as a major problem for their countries.

Note: Item No. 4 in this post was updated on March 23, 2018.

D'Vera Cohn is a senior writer/editor focusing on immigration and demographics at Pew Research Center.

Andrea Caumont is the digital engagement manager at Pew Research Center.