Following up on yesterday’s Keynesian Cross post:

1. The point, for those who missed it, is that using exactly the same reasoning that we find in Eco 101 textbooks to derive the Keynesian multiplier, we can conclude that sending all your money to me will make everyone rich. The conclusion is absurd; therefore the reasoning is invalid. And reasoning that’s invalid in one context is also invalid in another.
2. Some commenters thought that my version of the Keynesian cross argument was an unfair caricature. I invite those commenters to peruse some actual Eco 101 textbooks. For example, they might browse through the section labeled “The Income-Expenditure Model” in a widely used textbook called Macroeconomics. The authors are Robin Wells and Paul Krugman.
3. Let’s review the logic of that model. (See yesterday’s post for explanations of the notation.)

   Step I: Start with an accounting identity (in this case C+I+G).
   Step II: Throw in an empirical regularity (in this case C=.8Y).
   Step III: Combine the two equations to get a third equation (Y=5(I+G).)
   Step IV: Do a thought experiment involving a policy change (e.g. an increase in G) and predict the outcome by assuming that your equations will continue to hold after the policy change.

   By contrast, my alternative model starts with an accounting identity (Y=L+E), throws in an empirical regularity (Y=.999999E), combines these equations to get a third (Y=1000000L) and then predicts the outcome of a thought experiment (send me your money!) by assuming that the equations will continue to hold. In other words, yes, exactly the same logic.

4. The problem with the Landsburg multiplier story is that after you send me your money, the equation Y=.999999E is not likely to remain true. The problem with the Keynesian multiplier story is that after you increase government spending, the equality C=.8Y is not likely to remain true. Why not? Well, for one thing, if the government buys you a bowl of Wheaties, you’re correspondingly less likely to go out and buy a bowl of Wheaties for yourself. For another, if the government spends wastefully, you, as a taxpayer, are going to end up poorer, which means you’ll probably consume less. The exact nature of the change depends on the exact nature of the government spending. But there’s surely no reason to buy into the model’s assumption that there will be no change at all.

Continue reading ‘Multiple Comments’

Paul Krugman, defending the IS-LM (a/k/a “old Keynesian”) model of the macroeconomy as a non-rigorous but useful “scratchpad”, misses the point by a mile:

It’s a simplified model that more or less gets at what you think are the essentials of an issue, and is easy to work with, so you can use it to reach quick first-pass judgments about policy or whatever.

………

But IS-LM isn’t the prime example of a scratchpad. What is?

The answer is, supply and demand.

It is not easy to derive supply and demand curves for an individual good from general equilibrium with rational consumers blah blah. And it’s definitely not easy to justify consumer and producer surplus as measures of welfare. And there have always been some purists who condemn any use of the S and D curves we all grew up with, the use of triangles to measure welfare loss, and all that.

But for the most part nobody pays attention. The supply-and-demand framework is so convenient, while pretty much getting at what you want to get at, that it’s what almost everyone uses to get a first-pass analysis of economic issues.

Okay, look. Supply and demand (and, especially, triangles of welfare loss, etc) are not entirely rigorous, but they’re good useful simplifications that actually give useful (though approximate) answers to important policy questions. Sort of like Ohm’s Law for electrical circuits.

But IS-LM is not like that at all, because IS-LM does not even address the key policy questions in macroecomics. IS-LM can tell you, perhaps, how to fight a recession, but it can’t tell you whether the recession is worth fighting — not even loosely, because the model contains no individual utility functions and no social welfare function. It therefore does not allow you even to formulate the question of whether a given policy is worth its costs, because it provides no framework for weighing costs against benefits.

Continue reading ‘The Wrong Tool for the Job’

Okay, this one’s almost too bizarre for words. First, Paul Krugman makes an argument that ignores the existence of corporate dividends. Then, pretty much everybody in the world points out his error. Then, he admits his error, but, true to form, takes an irrelevant swipe at his critics. But in this case, the irrelevant swipe is: “Aha! You’ve just admitted that corporations pay dividends! So much for your past claims that corporations pay wages!”

Umm…Paul? They pay both. I’d lift Krugman’s own favorite dismissive phrase and say “That’s Economics 101”, but actually it’s probably standard knowledge among middle schoolers.

To review the details:

First, Krugman reposted (from the website of a left-wing advocacy group) a highly misleading chart purporting to illustrate the federal tax burdens borne by various income groups. The chart accounts for payroll and income taxes, but omits corporate taxes, thereby making the burden on high-income tax payers appear substantially smaller than it is, because corporate taxes reduce dividends which are disporportionately paid to high-income taxpayers.

Next, he got called on it by lots and lots of people, including, for example, Greg Mankiw.

Next, Krugman acknowledged his error. But, as always, he did so with the least possible grace, suggesting that his critics, by virtue of pointing out Krugman’s mistake, have somehow undermined their own principles.

In particular, his position is that by acknowledging that corporate profits benefit shareholders, “conservatives” have undermined their own ability to claim that corporations benefit anyone other than shareholders (e.g. workers). He relies, in other words, on the cockamamie notion that if something is good for group A, it can’t possibly also be good for group B.

Continue reading ‘In Which Paul Krugman Leaves Me At a Loss for Words’