The middle class that President Obama identified in his State of the Union speech last week as the foundation of the American economy has been shrinking for almost half a century.
In the late 1960s, more than half of the households in the United States were squarely in the middle, earning, in today’s dollars, $35,000 to $100,000 a year. Few people noticed or cared as the size of that group began to fall, because the shift was primarily caused by more Americans climbing the economic ladder into upper-income brackets.
But since 2000, the middle-class share of households has continued to narrow, the main reason being that more people have fallen to the bottom. At the same time, fewer of those in this group fit the traditional image of a married couple with children at home, a gap increasingly filled by the elderly.
This social upheaval helps explain why the president focused on reviving the middle class, offering a raft of proposals squarely aimed at concerns like paying for a college education, taking parental leave, affording child care and buying a home.
“Middle-class economics means helping working families feel more secure in a world of constant change,” Mr. Obama told Congress and the public on Tuesday.
Still, regardless of their income, most Americans identify as middle class. The term itself is so amorphous that politicians often cite the group in introducing proposals to engender wide appeal.
The definition here starts at $35,000 — which is about 50 percent higher than the official poverty level for a family of four — and ends at the six-figure mark. Although many Americans in households making more than $100,000 consider themselves middle class, particularly those living in expensive regions like the Northeast and Pacific Coast, they have substantially more money than most people.
However the lines are drawn, it is clear that millions are struggling to hang on to accouterments that most experts consider essential to a middle-class life.
“I would consider middle class to be people who can live comfortably on what they earn, can pay their bills, can set aside something to save for retirement and for kids in college and can have vacations and entertainment,” said Christine L. Owens, executive director of the National Employment Law Project, a left-leaning research and advocacy group.
The middle class has shrunk consistently over the past half-century. Until 2000, the reason was primarily because more Americans moved up the income ladder. But since then, the reason has shifted: There is a greater share of households on the lower rungs of the economic ladder.
Share of households
by income range:
53
45
43
40%
34
31
25
22
7
Low
Middle
High
< $35,000
–
20%
0%
’67
’13
Single
parent
Single adult
with no children
20%
0%
’67
’13
Geography also matters. The biggest declines in middle-class households during the previous half-century occurred in the Northeast — states like Massachusetts, Connecticut and New Jersey — where industrial economies gave way to mass suburbanization and increased affluence.
According to a New York Times poll in December, 60 percent of people who call themselves middle class think that if they work hard they will get rich. But the evidence suggests that goal is increasingly out of reach. When middle class people look up, they see the rich getting richer while they spin their wheels.
“The middle has basically stayed the same; it hasn’t improved,” said Lawrence F. Katz, an economist at Harvard University. “You’ve got an iPhone now and a better TV, but your median income hasn’t changed. What’s really changed is the penthouse has become supernice.”
Still, there are some recent signs of hope for the middle class. The economy is improving and more jobs are being created, many of them in better-paying categories like professional services, health care and even a reviving manufacturing sector.
See how your household income ranks in 344 zones across the United States.
Jason Pappas’s prospects, for example, are looking up. Mr. Pappas, 32, from Muncie, Ind., was earning about $42 an hour as an iron worker in the mid-2000s, but building projects dried up during the recession, pushing him onto the unemployment rolls for a year and a half.
He eventually found a job as a truck driver. Today, he earns just over half the hourly wage he made as an iron worker, but he is happy to have a steady job.
“It pays the bills,” he said, “and I have medical insurance.”
Moreover, Mr. Pappas just learned that he was being promoted to supervisor. Soon, with overtime, he’ll be earning $80,000 a year.
He is feeling a lot better about his future. “Hard work pays off,” Mr. Pappas said.
Marjorie Connelly contributed reporting.
A version of this article appears in print on January 26, 2015, on page B1 of the New York edition with the headline: More Fall Out as Middle Class Shrinks Further. Order Reprints| Today’s Paper|Subscribe
