Larry Summers exposes the flaw in Thomas Piketty’s Capital in the Twenty-First Century. Piketty argues that inequality is rising because the rate of return on capital is higher than the economy’s growth rate.
Does not the rising share of profits in national income in most industrial countries over the last several decades prove out Piketty’s argument? Only if one assumes that the only factors at work are the ones he emphasizes. Rather than attributing the rising share of profits to the inexorable process of wealth accumulation, most economists would attribute both it and rising inequality to the working out of various forces associated with globalization and technological change. For example, mechanization of what was previously manual work quite obviously will raise the share of income that comes in the form of profits. So does the greater ability to draw on low-cost foreign labor.
Correlation does not imply causation. The fact that two events occur together does not prove that one has caused the other.
Summers also addresses whether returns on capital are largely reinvested:
A brief look at the Forbes 400 list also provides only limited support for Piketty’s ideas that fortunes are patiently accumulated through reinvestment. When Forbes compared its list of the wealthiest Americans in 1982 and 2012, it found that less than one tenth of the 1982 list was still on the list in 2012, despite the fact that a significant majority of members of the 1982 list would have qualified for the 2012 list if they had accumulated wealth at a real rate of even 4 percent a year. They did not, given pressures to spend, donate, or misinvest their wealth. In a similar vein, the data also indicate, contra Piketty, that the share of the Forbes 400 who inherited their wealth is in sharp decline.
That income inequality is rising is undisputed, but the causes are not as simple as Piketty assumes. His proposal of a progressive tax on wealth is unlikely to see the light of day: the history of inheritance taxes is an indication of their ineffectiveness. But a shift away from income taxes towards land taxes and other flat rate, indirect taxes would provide a significant boost to the economy as illustrated by the following chart from the Henry Review.
Marginal welfare loss is the loss in consumer welfare per dollar of revenue raised for a small increase in each tax (the extent of compensation required to restore consumer satisfaction reflects the distorting effect of the tax on the economy). A decrease in the level of tax, on the other hand, would be likely to produce a similar-sized benefit. So a trade off between taxes at the top of the scale and those at the bottom would be expected to deliver a substantial net benefit.
Read more at Lawrence H. Summers for Democracy Journal: The Inequality Puzzle.