Why Income Is an Important Concept in Economics

By: Robert P. Murphy

At his entertaining blog, John Cochrane has a good thought experiment showing the flaws with conventional measures of income inequality. However, after making his great point, Cochrane summarizes by writing:

“Income” is really a fairly meaningless concept. We do not live in the Ancien Regime, or a Jane Austen novel in which people are described for life by the annual income they receive. Income varies a lot over a lifetime, and ebbs and flows for many. And “capital income” is not the same as earned income. The broad consensus theory of taxation states that capital income — the rate of return you get to induce you to save some income for future consumption rather than to blow it all right away — should not be taxed at all. It really isn’t “income” in any meaningful sense. [Cochrane, bold added.]

I am amazed when economists, frustrated with arguments over inequality, conclude that the very concept of “income” itself is meaningless. Long-time readers may remember that I wrote a long article at Mises.org on the issue when Scott Sumner wrote an entire post arguing that “income” was a “meaningless, misleading, and pernicious concept.” (What is it with the Chicago School that makes economists jettison the very concept of income?)

Contra Cochrane and Sumner, income is actually a critical concept. As Hayek explained in his Pure Theory of Capital, income can be defined as how much one can consume without depleting capital. All of these accounting relationships are of course integral to economic calculation, upon which—as Mises showed—civilization itself depends.

In this short blog post I won’t give a full rebuttal and explanation of what income is, and how it relates to lifetime consumption (which Cochrane and Sumner do think is a meaningful concept—thank goodness). Interested readers can refer to my earlier piece. For our purposes here, let me just use an analogy to show why Cochrane and Sumner are overreacting. Imagine a PhD nutritionist surveying all the fad diet crazes and exclaiming:

“Weight” is really a fairly meaningless concept. We don’t all have the same body types, and can’t be described by a single number. Weight varies a lot over a lifetime, and ebbs and flows for many. And “fat weight” is not the same as “muscle weight.” The broad consensus theory of health states that gaining muscle weight shouldn’t be penalized at all. It really isn’t “weight” in any meaningful sense.

Would the above make any sense at all? Would we excuse it by saying, “Oh, that nutritionist is just lashing out at the nonsense in the supermarket tabloids”? Of course not; we would just insist that the experts chide the novices for superficial discussions, and ask them for more nuanced analyses.

Likewise, just because politicians try to justify higher taxes through ludicrous abuses of statistics, doesn’t mean the very concept of “income” is meaningless.

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