“If preferences are subjective to each individual, and cannot even be measured or quantified for each individual, then obviously it would make no sense at all to try to combine or aggregate individual preferences into ‘social’ preferences. Unfortunately, even professional economists often engage in just this type of reasoning. Many people (try to) justify progressive income taxation, for example, by claiming that ‘a dollar means more to a poor man than to a rich man.’ The idea is that taking $1 million from Bill Gates won’t lower his utility very much, whereas handing out $1,000 to a thousand different homeless people will greatly boost each of their utilities. Therefore, the typical argument goes, total or “social” utility has been increased by the redistribution of some of Bill Gates’s wealth.The trouble with this is that, just because it is impossible to aggregate the subjective utilities of different people or find some objective unit of measurement with which to make objective interpersonal utility comparisons, it does not follow that an economic argument for progressive income taxes, on basis of diminishing marginal subjective utility, has failed.
… For now, we point out that the typical justification for it is absurd. You can’t add up different amounts of utility from various people. In fact, if you use the alternate term preferences it will be more apparent why combining them from different people is an impossible task.” (Murphy 2010: 42).
Of course, there are problems with the so-called “law” of diminishing marginal subjective utility, as I have shown here, but there is reason to think it is true as a generalised statement.
If any Austrian economist accepts the “law” of diminishing marginal utility (or accepts it merely as a general principle), it follows that a very rich person should, generally speaking, derive less utility from an extra dollar than a person who is very poor, even if one cannot measure the utility in some objective quantity like “utils.”
If indeed there is good reason to think that the value of an additional unit of income to a person who is already very rich is considerably less than the value of an additional unit to someone who is poor, then redistribution of income to promote happiness and reduce hardship has sound economic justification.
And indeed empirical evidence seems to show that as wealth rises, the happiness that one derives from additional income falls or levels off after about $70,000 (US) (e.g., a fascinating discussion of this topic here).
Curiously, it was none other than the Austrian economist Friedrich von Wieser who prided himself on having provided a solid economic justification for progressive taxation on the basis of diminishing marginal utility. Modern Austrians apparently choose to forget this embarrassing fact.
The argument against progressive taxation that we cannot objectively “measure” the utility lost by the rich man as compared with that gained by the poor man does not necessarily refute the argument from diminishing marginal utility: for it requires a highly unrealistic assumption, as we shall now see.
If we were to take two poor people both with the same income, and imagine one becoming extremely rich while the other remains poor, the argument against progressive income tax could only work if the utility the rich man derived from a unit of money while poor was vastly – and indeed unrealistically and extremely – greater than that of his fellow, so that as each additional unit of money the man received – even to very high levels like millions or billions of dollars – the diminished utility still remained so high that it exceeded that of his fellow who still remained poor.
Now of course individuals display variation and can and do have different degrees of subjective utility in terms of the satisfaction that they derive from any good x (and even from a unit of money), but to believe that all or most rich people derive greater utility from one unit of their money than a poor person from one extra unit again requires the ridiculous assumption that, if (hypothetically) or when (in reality) they were poor, all or most of these rich people derived a degree if utility vastly – and indeed unrealistically and extremely – greater than that of other poor people.
This, quite frankly, violates everything we know about human psychology, neuroscience and evolution. Human beings are all products of Darwinian evolution; they have the same fundamental biochemistry and neural processes in the brain; the mind and all its emotions, like happiness, satisfaction and pleasure, are causally dependent on brain processes. People do display individual variation in many traits – such as height, eye colour, and no doubt in what economists call utility – but not to the extent that average people have such a vast difference between them as would be required in the case we have imagined above.
But we need only think of height here. Most human beings have a height between 5 feet and 6 feet, and even exceptions (apart from highly usually things like dwarfism and gigantism) do not deviate too far from this range. Height is a product of genetics and environmental influences. There is every reason to think that the propensity to feel emotions like happiness, satisfaction and pleasure – the emotions that the word “utility” in an economic sense describes – are a product of genetics and environmental influences too, with individual variation, but not so vast that the utility felt by two average people while poor is so vastly different that one million dollars or $100 million – under the principle of diminishing marginal utility – given to one man would still not reduce his utility from one extra dollar to a level below that experienced by the other poor man from one extra dollar.
In short, Austrians, like neoclassicals, if they really accept the “law” of diminishing marginal utility without the ridiculous assumption we have identified above, then the economic argument for progressive taxation from diminishing marginal utility is hard to refute.
Of course, they might make a moral argument from Rothbardian natural rights or Hoppe’s argumentation ethics, but this is clearly a different type of argument from the one based on subjective utility.
Murphy, Robert P. 2010. Lessons for the Young Economist. Ludwig von Mises Institute, Auburn, Ala.