Editors’ note: This post is the first of two parts about a leftward shift in American politics.

The Democratic Party has moved left in recent years. Evidence from 2000, 2004 and 2008 suggests that until then, the party’s positions on a wide range of issues were like those of many center-right parties in other rich democracies. But starting in 2012, the Democrats began shifting left — and by 2016, were more in line with center-left parties elsewhere. In the current Democratic presidential primary, the front-runners’ proposals — including those of centrist former vice president Joe Biden — are to the left of the party’s 2016 positions. That’s consistent with the views of Democratic voters, who have also shifted left.

But Democratic voters are hardly outliers. On cultural issues and government social programs, the United States as a whole has been moving left for decades. I’ll explain below.

1. Affluent societies shift left on cultural issues

Many observers believe the United States is in an endless culture war, with neither progressives nor conservatives gaining a lasting advantage. That’s not so. Every noteworthy cultural shift over the past half-century — on race, gender roles, families, sexual orientation, gender presentation, drugs and more — has moved the country in the direction of greater personal freedom. Not only Democrats have moved to left; Republicans have, too. While abortion might seem an exception, public opinion on this issue hasn’t shifted to the right, and Americans’ growing access to “medical” abortion via the mifepristone and misoprostol pills — which were used for 39 percent of abortions in 2017, up from 1 percent in 2000 — has helped offset new restrictions on surgical abortions in conservative states.

This is predictable. Drawing on half a century of public opinion survey data from multiple countries, Ronald Inglehart and Christian Welzel have found that as societies get richer, people tend to shift away from a worldview that emphasizes traditional authority, religious dictates, social roles and the well-being of the group or community over that of the individual. They increasingly view all people, including members of disfavored groups, as equally worthy of rights, opportunities and respect. They also increasingly prioritize personal liberty. Most people, whether in an affluent society or a poor one, want the freedom to choose what to believe, how to behave, with whom to live, and so on. As a community’s level of material well-being increases, this desire for freedom becomes more prominent.

2. Well-off countries tend to offer more public benefits

Rising affluence also brings more expansive and generous government social programs. The higher someone’s income, the more insurance they are generally willing to buy to minimize potential loss. Governments are the most efficient source of some kinds of insurance. Think of income in old age: Voluntary savings clubs could help people set money aside for retirement, but a public pension program does that more effectively and efficiently. So as countries get richer the welfare state tends to grow.

That includes the United States’ welfare state, which has kept expanding, if slowly — even through the Reagan era and beyond. True, the United States now offers less money to fewer people through its main assistance program for poor families: TANF, or Temporary Assistance for Needy Families, formerly AFDC, or Aid to Families With Dependent Children.

But at the same time, the U.S. government has expanded many other programs. The average Social Security benefit, adjusted for inflation, increased from $11,500 in 1980 to $17,000 in 2017. The Earned Income Tax Credit, a program created in 1975 to boost the income of low-earning households, has been expanded to cover 23 percent of Americans, up from 8 percent in 1980. Its two main disability benefits, Social Security Disability Insurance (SSDI) and Supplemental Security Income (SSI), reach 5 percent of Americans, up from 2 percent in 1980. Medicare and Medicaid now insure about 40 percent of Americans, double the share in 1980.

Aggregate indicators paint a similar picture. Among households in the bottom fifth of incomes, the average amount of government transfers received minus taxes paid, adjusted for inflation, rose from $7,300 in the 1980s to $9,400 in the 2010s. Government expenditures on social programs rose from 13 percent of GDP in 1980 to 19 percent in 2018.

As you can see in the chart below, while the United States offers less assistance than do Denmark and Sweden, it has been expanding for most of the past century. The difference between those two countries, known for their generosity, and the United States today is much smaller than the difference between the United States today and a century ago.

Some states have jumped well ahead of the federal government in their social programs’ reach and generosity. Since 1999, California has enacted paid sick leave; paid parental leave; an automatic-enrollment pension system for people whose employers don’t offer plans; expanded Medicaid coverage and TANF eligibility; a state Earned Income Tax Credit that supplements the federal EITC; tuition-free community college; low-cost public auto insurance for individuals with low income, and more. The state of New York has adopted paid sick leave, paid family leave and tuition-free public college for in-state students from middle- and lower-income households. Its largest city offers universal preschool for 4-year-olds and will soon add 3-year-olds. Massachusetts, Washington and Oregon have been moving in a similar direction. Massachusetts’ 2008 health-care reform reduced its uninsured rate to 2.8 percent, the country’s lowest; Washington has a new “public option” for health insurance; Oregon has added paid family leave and free community college. Nearly 80 million people, 1 in 4 Americans, live in these five states.

But haven’t conservative states gone in the opposite direction, shrinking government social programs rather than expanding them? As political scientist Matt Grossman has documented, most conservative states in recent decades have either offered slow increases or no change, rather than reductions. In a few instances, such as universal preschool for 4-year-olds in Oklahoma and Georgia and free community college in Tennessee, these states have led in expanding social policy.

3. The American public dislikes ‘big government’ but likes social programs

Many Americans dislike the idea of big government. Between 55 and 75 percent regularly say they agree that “When something is run by the government, it is usually inefficient and wasteful,” according to the Pew Research Center. But once new social programs are enacted, Americans tend to support them.

Again, that’s not just Democrats. Donald Trump’s success in the Republican primary race in 2016 owed partly to the fact that he was, as he tweeted in May 2015, “the first & only potential GOP candidate to state there will be no cuts to Social Security, Medicare & Medicaid.” When President Trump abandoned this pledge and joined congressional Republicans in trying to pare back Medicaid coverage, it was the least popular major legislative proposal since 1990.

America hasn’t moved to the left on all issues. But the country’s progressive turn on cultural issues and government social programs is real, long-run, broad-based and unsurprising.

Editors’ note: This post is the first of two parts about a leftward shift in American politics. Part 2 can be found here.

Lane Kenworthy is professor of sociology and Yankelovich Chair in Social Thought at the University of California at San Diego. His most recent book is “Social Democratic Capitalism” (Oxford University Press, 2019).