Monthly Archive for May, 2014

On Piketty and Capital

Important disclaimer: I have not read Thomas Piketty‘s book on Capital in the Twenty-First Century, and therefore cannot possibly have given it a fair reading.

I do, however, trust Per Krusell and Tony Smith to have given it a fair reading, because Krusell and Smith have long track records as diligent and thoughtful scholars. And their analysis appears to devastate both Piketty’s model and his prediction that income inequality is destined to grow explosively over time.

Here’s why:

All of Piketty’s predictions depend on his assumptions about how much people save. The simplest respectable model (that is, a model that economists generally feel comfortable using for many purposes, and which fits fairly well with observations) says that we save a fixed percentage of our incomes — say 30%. (There are also more sophisticated models in which this percentage can change as economic conditions change.)

Piketty, by contrast, assumes that our net saving is a fixed percentage of our net incomes, where “net” means “after subtracting depreciation of our assets”. That’s a very different assumption, and, according to Krusell and Smith, not at all a plausible one. It’s implausible first because it has extremely odd implications. Most notably, it implies (though this is not immediately obvious) that if economic growth slows to zero, we will eventually choose to save 100% of our incomes(!!). Beyond that, Krusell and Smith argue in considerable detail that, compared to the more traditional models, Piketty’s does a poor job of fitting the last seventy years’ worth of data.

According to Krusell and Smith, Piketty demonstrates correctly that under his assumptions, slowing economic growth must lead to massive inequality over time. But under the far more plausible assumptions found in modern textbooks and modern research papers, that conclusion goes away. In fact, after substituting those assumptions, Piketty’s arguments yield something like the opposite conclusion — as growth slows down, changes in inequality become pretty much negligible.

If this analysis is right — and given the identities of the authors I’ll be very surprised if it’s wrong — then there appears to be very little reason to buy into Piketty’s story. That doesn’t mean he’s wasted his time. We learn a lot by making a variety of different assumptions and figuring out where they lead us, even when the assumptions are ultimately unsupportable. But a serious intellectual exercise is not the same thing as a serious prediction.


The Rising Tide

So the Obama administration has released a climate forecast, according to which Miami could be under water by the end of the century. Apparently we’re supposed to be very concerned about that.

To put this in perspective, we’ve currently got about 140,000,000 square miles of ocean on this planet — about 71.066% of the earth’s surface. Add Miami’s 35 square miles and that goes up to 71.066007%. You could add all of South Florida and barely notice the difference.

Here’s what Jeff Goodell of Rolling Stone says about that:

Of course, South Florida is not the only place that will be devastated by sea-level rise. London, Boston, New York and Shanghai are all vulnerable, as are low-lying underdeveloped nations like Bangladesh. But South Florida is uniquely screwed, in part because about 75 percent of the 5.5 million people in South Florida live along the coast.

What Mr. Goodell appears to overlook is that of the 5.5 million people now living in South Florida, approximately zero will be alive a hundred years from now, and those that are will presumably have had the sense to move inland well before the water reaches their breastbones.

Continue reading ‘The Rising Tide’

Something to Celebrate

Here’s a key lesson of economics: Trade is good, but trade with people very unlike yourself is even better. I’m a teacher who eats beef, drives a car and lives in a house. I don’t need other teachers so much as I need students, ranchers, autoworkers and architects. If your neighbors love gardening as much as you hate it, you’ll find it easy to hire a gardener. If it’s the other way around, you’ll do well in the gardening business.

The lesson spills over beyond the markets for goods and services. We learn new ways of thinking and new ways of living from people who think and live differently than ourselves.

We thrive on diversity — diversity of skills, diversity of interests, diversity of lifestyles, diversity of religious and political outlooks, diversity of culinary and artistic tastes, diversity of lifestyles, and, lest we forget, diversity of income. Capitalists need workers and workers need capitalists. A wealthy factory owner won’t stay wealthy for long if here’s nobody to work the assembly lines. A middle-class assembly line worker won’t be middle-class for long if there’s nobody building factories.

Let us then celebrate diversity, not try to extinguish it. And let’s not forget that diversity of income — or, if you prefer, “income inequality” — is just as much a blessing as diversity of skills, preferences, cultural outlooks, and ways of living.

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Housing Problems

Josh Barro observes that home ownership is a really bad investment strategy insofar as it involves putting an awful lot of eggs in one basket — indeed, for many people it involves putting more eggs than they’ve got in one basket, since the mortgage market allows you to sink more than your entire net worth into a single house.

In fact, it’s even worse than Josh says. If your house is located anywhere near your workplace (in other words, if you’re almost anyone) then a local economic downturn can devastate your home value at exactly the same time that it’s costing you your job. That’s a whole lot of unnecessary risk.

As Josh acknowledges, that doesn’t mean you shouldn’t own a house; it just means you shouldn’t fool yourself into thinking it’s a wise investment.

But Dan McLaughlin at the Federalist isn’t satisfied:

Economists … should never make the mistake of ignoring consumer behavior they regard as irrational…What Barro should have asked himself (as any real economist should) before declaring that vast numbers of homebuyers and homeowners have been acting irrationally for millenia in buying their own homes is: what are they getting out of it that my analysis is missing?

I enthusiastically endorse the sentiment that when we observe “inexplicable” behavior, our first instinct should be to ask “What am I missing?”. But Barro at least tried to do that — he pointed to “a sense of security” and the desire to customize one’s residence. I agree with McLaughlin’s assessment that these are pretty weak answers, but unfortunately McLaughlin’s own “answers” are even weaker. According to McLaughlin, we own houses because we don’t like to move, and he elaborates at length on the reasons why —- moving is expensive, it means adjusting to new neighborhoods, uprooting your family, etc. etc.

The thing is, though, none of this is a reason to own rather than rent. You could accomplish all of the above with a 99-year lease (binding for the landlord but not for the tenant) which would give you all the residential stability of home ownership while transferring the risk to a professional landlord with diversified holdings.

So why do people buy houses? Offhand, I can think of three answers:

Continue reading ‘Housing Problems’

Social Accounting

We’ve had a very long recent thread about the social costs and benefits of high frequency trading, where I’ve apparently managed to confuse a number of readers by switching back and forth, according to the convenience of the moment, between two different, but perfectly legitimate, social accounting systems.

To clarify matters, let’s forget for the moment about high frequency trading and look at something simpler — innovation in the IT industry, where it’s clear that profit-maximization can easily lead to too much innovation. I’ll do the accounting both ways to make it clear that both ways are right.

First, the assumptions:

Alice has developed a word processor, which she sells online. It costs her $5000 a year to maintain a server, where you can download a copy for $1000. She sells 100 copies a year, and therefore collects $100,000 in revenue. Most of the consuemrs who buy those copies value them at more than their price. In fact, the total value of those 100 copies to the consumers is $200,000.

Bob has an idea for a word processor that’s a little better than Alice’s, so that each consumer would be willing to pay $10 more for Bob’s than for Alice’s.

If Bob develops his word processor, how much can Alice charge for hers? Because her word processor is inferior to Bob’s, she’s got to undercut his price by $10 in order to maintain any customers at all. So if Bob charges $600, Alice charges $590. But then Bob can steal all of Alice’s customers by lowering his price to $599.99, whereupon Alice must lower her price to $589.99, whereupon Bob steals all her customers by lowering his price another penny….and the race to the bottom is on. But Alice’s price cannot fall below $50, because then she wouldn’t earn enough to cover her server costs. So Alice, who is smart enough to foresee all this, gives up and cedes the market to Bob.

Once Bob has the market to himself, he doesn’t have to worry about re-entry by Alice, because they both know perfectly well that the instant she renews her server contract, the race to the bottom will be back on and she’ll have spent $5000 for nothing.

Now if Bob sells his word processor for $1000, it’s he instead of Alice who earns $100,000 a year in revenue and therefore (after subtracting the server cost) $95,000 in profit. He weighs this against the $80,000 cost of developing his word processor and takes the plunge.

I claim that Bob’s decision is privately wise (i.e. wise from Bob’s point of view) and socially foolish (i.e. it reduces social welfare, defined as the total dollar value of all the gains to consumers and producers). We can calculate the costs and benefits of Bob’s decision in either of two equally legitimate ways. Because they are equally legitimate, they lead to the same bottom line: Bob’s private benefit exceeds his private cost by $15,000 (which is why he plunges ahead), while the social cost exceeds the social benefit by $79,000 (which is why we wish he wouldn’t).

Continue reading ‘Social Accounting’