Capital in the Twenty-First Century

Piketty argues that inequality is not an accident but a feature of capitalism that can be reversed only through state intervention, and that unless capitalism is reformed, democratic order is threatened [citation:2]. He rejects Simon Kuznets's optimistic 'fairy tale' that capitalism has a built-in trend toward greater equality. Piketty demonstrates that the decline in inequality during the postwar period was the exception, caused by two world wars and the Great Depression, not the rule. The rule is that r > g drives ever-increasing concentration of wealth [citation:5].

Piketty's famous formula is r > g, where r is the rate of return on capital and g is the rate of economic growth. When r substantially exceeds g, wealth accumulated in the past grows faster than output and wages, and inequality of wealth tends to rise to very high levels [citation:9]. Piketty himself later clarified that r > g is not the only tool for analyzing inequality—institutional changes and political shocks also play major roles [citation:19]. The formula has become a standard reference in debates over wealth taxes and inequality measurement.

Gerald Auten and David Splinter have led a significant challenge, finding that trends in income inequality are far less dramatic once taxes and transfers are accounted for. They estimate the top 1 percent received about 9 percent of post-tax-and-transfer income in the 1960s and 10 percent in the early 2020s, with a low ebb of about 7 percent in the 1970s [citation:13]. The dispute hinges on methodological choices, particularly how 'missing income' not reported on tax returns is allocated across the distribution. Piketty's camp allocates more of this income to top earners.

Piketty's second fundamental law states that the capital/income ratio is determined by the savings rate divided by the growth rate, predicting that wealth-to-income ratios rise dramatically as growth slows. Krusell and Smith argue this law rests on a theory of saving that is difficult to justify—it implies an unrealistic 100% savings rate at the lowest rate of growth [citation:18]. Using standard alternative theories, they show that if growth fell by half, the capital-to-output ratio would increase only modestly, not dramatically as the second law predicts.

Piketty argues that a progressive global tax on capital is necessary to prevent an endless inegalitarian spiral and to preserve democratic sovereignty. He acknowledges it is politically difficult but insists progress can be made at national and regional levels first. As he told IPPR, 'it doesn't have to be global—a lot of progress can be made at the national level,' including transforming traditional property taxes into progressive taxes on net wealth [citation:4]. He notes that five years ago people said nothing would happen on tax havens, yet the US sanctions against Swiss banks produced results [citation:4].

Many readers and commentators call Piketty a 'modern Marx,' but Piketty explicitly rejects Marx's central conclusion. Marx predicted the rate of return would tend toward zero, culminating in a final catastrophe with a falling rate of profit. Piketty states: 'I don't think there is any good historical evidence for this claim and there is no logical consistency behind it either' [citation:9]. He does not predict a big catastrophe, though he warns that growing inequality can raise serious political problems. The book's title echoes Marx, but its argument is fundamentally different.