K21

r = the return on wealth
s = savings rate
depreciation of capital?
capital share of economy?

Kuznets, happy trickle-down equalizing capitalism where capital and labor share income? Solow growth model?

Matt Breunig's take? Solow's take? Krugman's take? DeLong's finger exercises? Baker's take? Henwood's take? Boushey's take? Waldman's take? Suresh Naidu?

the mechanism by which the savings rate declines (and r declines) as the capital/income ratio increases and growth slows.

As growth slows, will the "savings rate" decline automatically. Will "r" the return on capital decline. What about rents? How does depreciation fit into the equation. Is this DeLong's Hicks on Piketty's Keynes?

How does the wealth to income ratio increase? What were the growth rates in pre-WWI capitalism?

Henwood:

It was once believed, during the decades immediately following the Great Depression and World War II, that vast disparities in wealth were features of youthful capitalism that had been left behind now that the thing was reaching maturity. This theory was first enunciated formally in a 1955 paper by the economist Simon Kuznets, who plotted a curve representing the historical course of inequality that looked like an upside-down U: Kuznets’s chart showed that disparities in wealth rose dramatically during the early years of growth and then reversed once a mature capitalist economy reached a certain (though none-too-specific) stage of development.

Kuznets’s curve fit nicely with the actual experiences of the rich economies in what the French call the Trente Glorieuses, the “thirty glorious years” between 1945 and 1975, when economic growth was broadly shared and income differentials narrowed. In the United States, according to the Census Bureau’s numbers (which have their problems—more on that in a moment), the share of income claimed by the top 20 percent—and within that group, the top 5 percent—declined during the glorious years. At the same time, the income of the remaining 80 percent gained.

But in the United States, the thirty glorious years were actually twenty-odd years; depending on how you measure it, the equalization process ended sometime between 1968 and 1974, again according to the census figures. Still, quibbles aside, the process of relative equalization went on for long enough that it felt like Kuznets was on to something with his curve. I say “relative” because these are still not small numbers: The richest 5 percent of families had incomes about eleven times those of the poorest 20 percent in 1974, the most equal year by this measure since the census figures started in 1947. But that number looks small now compared with the most recent ratio, almost twenty-three times in 2012.

Krugman:

Just about all economic models tell us that if g falls—which it has since 1970, a decline that is likely to continue due to slower growth in the working-age population and slower technological progress—r will fall too. But Piketty asserts that r will fall less than g. This doesn’t have to be true. However, if it’s sufficiently easy to replace workers with machines—if, to use the technical jargon, the elasticity of substitution between capital and labor is greater than one—slow growth, and the resulting rise in the ratio of capital to income, will indeed widen the gap between r and g. And Piketty argues that this is what the historical record shows will happen. 

If he’s right, one immediate consequence will be a redistribution of income away from labor and toward holders of capital. The conventional wisdom has long been that we needn’t worry about that happening, that the shares of capital and labor respectively in total income are highly stable over time. Over the very long run, however, this hasn’t been true. In Britain, for example, capital’s share of income—whether in the form of corporate profits, dividends, rents, or sales of property, for example—fell from around 40 percent before World War I to barely 20 percent circa 1970, and has since bounced roughly halfway back. The historical arc is less clear-cut in the United States, but here, too, there is a redistribution in favor of capital underway. Notably, corporate profits have soared since the financial crisis began, while wages—including the wages of the highly educated—have stagnated. 

A rising share of capital, in turn, directly increases inequality, because ownership of capital is always much more unequally distributed than labor income. But the effects don’t stop there, because when the rate of return on capital greatly exceeds the rate of economic growth, “the past tends to devour the future”: society inexorably tends toward dominance by inherited wealth.

Naidu: "Every economics student learns the “Kaldor facts” of economic growth. One of these is that the share of national income going to capital has a long-run tendency to stay constant."

"But what keeps r high? Piketty never explicitly says. This question is at the heart of the struggle over how to interpret his book."
Solow:

"Suppose we accept Piketty’s educated guess that the capital-income ratio will increase over the next century before stabilizing at a high value somewhere around 7. Does it follow that the capital share of income will also get bigger? Not necessarily: remember that we have to multiply the capital-income ratio by the rate of return, and that same law of diminishing returns suggests that the rate of return on capital will fall. As production becomes more and more capital-intensive, it gets harder and harder to find profitable uses for additional capital, or easy ways to substitute capital for labor. Whether the capital share falls or rises depends on whether the rate of return has to fall proportionally more or less than the capital-income ratio rises. 

There has been a lot of research around this question within economics, but no definitely conclusive answer has emerged. This suggests that the ultimate effect on the capital share, whichever way it goes, will be small. Piketty opts for an increase in the capital share, and I am inclined to agree with him. Productivity growth has been running ahead of real wage growth in the American economy for the last few decades, with no sign of a reversal, so the capital share has risen and the labor share fallen. Perhaps the capital share will go from about 30 percent to about 35 percent, with whatever challenge to democratic culture and politics that entails."

DeLong's question: ""But if the savings rate necessarily falls as the wealth-to-annual-net-income ratio rises, why was the (gross) savings rate half again as high back before World War I when the economy was wealth-dominated as it is today?""

Going through the reviews.

Juncture interview:
"My bottom line is that the average rate of return for all assets combined is not going to zero. It has been going down a little bit over the past 20 to 30 years because of the rise in the capital-to-income ratio, but it has declined less than the increase in the capital–income ratio, so that the capital share has actually increased."

On Summers' stagnation:

"I think that here there is some confusion in these critiques between the interest rate and the rate of return to capital. The rate of return to capital is a much broader concept than just interest rates. If the rate of return on capital were really going to zero, as Summers seems to argue, then the capital share in GDP and the capital share in the economy would be going to zero. This has not been happening at all. Right now, including five years of total crisis, the capital share is much higher than it was twenty years ago in most developed countries.

So, what’s in the capital share? With the capital share you can have interest payment, dividends, corporate profits (with some of it going into retained earnings which feeds capital gains), and you have rental income. If you make a sum of all these forms of capital payment, then the capital share has not been going to zero at all.

I think that it is just wrong to take the interest rate on public debt as an indicator of the rate of return. Public debt is a very particular kind of asset: it provides liquidity services – that is, you can easily sell your Treasury bonds – and that is partly why people accept having relatively low returns in comparison to other assets. Also, we are not completely out of the financial crisis yet and we have had a lot of creative monetary policies that have kept interest rates low.

I think that where Summers is right, and this is where he wants to get, is that we have been asking too much of creative monetary policies in recent years, pretty much everywhere – in the US, in the UK, and in the Eurozone – because at the end of the day we have this very low interest rate on some assets such as public debt or certain categories of short-term or medium-term loans, but this is creating bubbles in other assets "