In 1930, the English economist John Maynard Keynes took a break from writing about the problems of the interwar economy and indulged in a bit of futurology. In an essay entitled “Economic Possibilities for Our Grandchildren,” he speculated that by the year 2030 capital investment and technological progress would have raised living standards as much as eightfold, creating a society so rich that people would work as little as fifteen hours a week, devoting the rest of their time to leisure and other “non-economic purposes.” As striving for greater affluence faded, he predicted, “the love of money as a possession . . . will be recognized for what it is, a somewhat disgusting morbidity.”

This transformation hasn’t taken place yet, and most economic policymakers remain committed to maximizing the rate of economic growth. But Keynes’s predictions weren’t entirely off base. After a century in which G.D.P. per person has gone up more than sixfold in the United States, a vigorous debate has arisen about the feasibility and wisdom of creating and consuming ever more stuff, year after year. On the left, increasing alarm about climate change and other environmental threats has given birth to the “degrowth” movement, which calls on advanced countries to embrace zero or even negative G.D.P. growth. “The faster we produce and consume goods, the more we damage the environment,” Giorgos Kallis, an ecological economist at the Autonomous University of Barcelona, writes in his manifesto, “Degrowth.” “There is no way to both have your cake and eat it, here. If humanity is not to destroy the planet’s life support systems, the global economy should slow down.” In “Growth: From Microorganisms to Megacities,” Vaclav Smil, a Czech-Canadian environmental scientist, complains that economists haven’t grasped “the synergistic functioning of civilization and the biosphere,” yet they “maintain a monopoly on supplying their physically impossible narratives of continuing growth that guide decisions made by national governments and companies.”

Once confined to the margins, the ecological critique of economic growth has gained widespread attention. At a United Nations climate-change summit in September, the teen-age Swedish environmental activist Greta Thunberg declared, “We are in the beginning of a mass extinction, and all you can talk about is money and fairy tales of eternal economic growth. How dare you!” The degrowth movement has its own academic journals and conferences. Some of its adherents favor dismantling the entirety of global capitalism, not just the fossil-fuel industry. Others envisage “post-growth capitalism,” in which production for profit would continue, but the economy would be reorganized along very different lines. In the influential book “Prosperity Without Growth: Foundations for the Economy of Tomorrow,” Tim Jackson, a professor of sustainable development at the University of Surrey, in England, calls on Western countries to shift their economies from mass-market production to local services—such as nursing, teaching, and handicrafts—that could be less resource-intensive. Jackson doesn’t underestimate the scale of the changes, in social values as well as in production patterns, that such a transformation would entail, but he sounds an optimistic note: “People can flourish without endlessly accumulating more stuff. Another world is possible.”

Even within mainstream economics, the growth orthodoxy is being challenged, and not merely because of a heightened awareness of environmental perils. In “Good Economics for Hard Times,” two winners of the 2019 Nobel Prize in Economics, Abhijit Banerjee and Esther Duflo, point out that a larger G.D.P. doesn’t necessarily mean a rise in human well-being—especially if it isn’t distributed equitably—and the pursuit of it can sometimes be counterproductive. “Nothing in either our theory or the data proves the highest G.D.P. per capita is generally desirable,” Banerjee and Duflo, a husband-and-wife team who teach at M.I.T., write.

The two made their reputations by applying rigorous experimental methods to investigate what types of policy interventions work in poor communities; they conducted randomized controlled trials, in which one group of people was subjected to a given policy intervention—paying parents to keep their children in school, say—and a control group wasn’t. Drawing on their findings, Banerjee and Duflo argue that, rather than chase “the growth mirage,” governments should concentrate on specific measures with proven benefits, such as helping the poorest members of society get access to health care, education, and social advancement.

Banerjee and Duflo also maintain that in advanced countries like the United States the misguided pursuit of economic growth since the Reagan-Thatcher revolution has contributed to a rise in inequality, mortality rates, and political polarization. When the benefits of growth are mainly captured by an élite, they warn, social disaster can result.

That’s not to say that Banerjee and Duflo are opposed to economic growth. In a recent essay for Foreign Affairs, they noted that, since 1990, the number of people living on less than $1.90 a day—the World Bank’s definition of extreme poverty—fell from nearly two billion to around seven hundred million. “In addition to increasing people’s income, steadily expanding G.D.P.s have allowed governments (and others) to spend more on schools, hospitals, medicines, and income transfers to the poor,” they wrote. Yet for advanced countries, in particular, they think policies that slow G.D.P. growth may prove to be beneficial, especially if the result is that the fruits of growth are shared more widely. In this sense, Banerjee and Duflo might be termed “slowthers”—a label that certainly applies to Dietrich Vollrath, an economist at the University of Houston and the author of “Fully Grown: Why a Stagnant Economy Is a Sign of Success.”

As his subtitle suggests, he thinks that slower rates of economic growth in advanced countries are nothing to worry about. Between 1950 and 2000, G.D.P. per person in the U.S. rose at an annual rate of more than three per cent. Since 2000, the growth rate has slowed to about two per cent. (Donald Trump has not, as he promised, boosted over-all G.D.P. growth to four or five per cent.) The phenomenon of slow growth is often bemoaned as “secular stagnation,” a term popularized by Lawrence Summers, the Harvard economist and former Treasury Secretary. Yet Vollrath argues that slower growth is appropriate for a society as rich and industrially developed as ours. Unlike other growth skeptics, he doesn’t base his case on environmental concerns or rising inequality or the shortcomings of G.D.P. as a measurement. Rather, he explains this phenomenon as the result of personal choices—the core of economic orthodoxy.

Vollrath offers a detailed decomposition of the sources of economic growth, which uses a mathematical technique that the eminent M.I.T. economist Robert Solow pioneered in the nineteen-fifties. The movement of women into the workplace provided a onetime boost to the labor supply; in its aftermath, other trends dragged down the growth curve. As countries like the United States have become richer and richer, Vollrath points out, their inhabitants have chosen to spend less time at work and to have smaller families—the result of higher wages and the advent of contraceptive pills. G.D.P. growth slows when the growth of the labor force declines. But this isn’t any sort of failure, in Vollrath’s view: it reflects “the advance of women’s rights and economic success.”

Vollrath estimates that about two-thirds of the recent slowdown in G.D.P. growth can be accounted for by the decline in the growth of labor inputs. He also cites a switch in spending patterns from tangible goods—such as clothes, cars, and furniture—to services, such as child care, health care, and spa treatments. In 1950, spending on services accounted for forty per cent of G.D.P.; today, the proportion is more than seventy per cent. And service industries, which tend to be labor-intensive, exhibit lower rates of productivity growth than goods-producing industries, which are often factory-based. (The person who cuts your hair isn’t getting more efficient; the plant that makes his or her scissors probably is.) Since rising productivity is a key component of G.D.P. growth, that growth will be further constrained by the expansion of the service sector. But, again, this isn’t necessarily a failure. “In the end, that reallocation of economic activity away from goods and into services comes down to our success,” Vollrath writes. “We’ve gotten so productive at making goods that this has freed up our money to spend on services.”