Excerpt from: Measuring the Immeasurable
Wealth is a meaningless term without the concept of value. If we know that the purpose of human action is to satisfy one's needs and wants, then the material wealth of two different individuals (let alone abstract entities such as nations) cannot tell us much about the satisfaction of their needs and wants. Wants and needs are subjective, unknown, and immeasurable by an outside observer.
We should thus be careful when interpreting empirical observations related to the quantity of goods and services produced in an economy. This is not to say that the GDP cannot tell us anything about a region. It simply means that GDP cannot tell us much about some of the most important economic concepts, such as value and economic success.
Most of today's economists endorse the subjective theory of value. According to this theory, the value of anything exists only in the mind of an individual. Thus, values held by two individuals cannot be compared except by observing an act of exchange. And even then, we can only make somewhat obvious statements — for instance, that in his exchange Jim values good A more than x dollars, while Janis values good A less than x dollars. To take it a step further, stating that Jim values good A more than Janis values good A simply lacks logical meaning.
There is no unit of measurement for value and no apparatus that can compare how much something is worth to two different individuals. This is the principle of the interpersonal incomparability of utility. Individual value scales cannot be superimposed and quantitatively compared. Since subjective value cannot be objectively measured, it cannot be objectively added, divided, or multiplied across individuals. Consequently, GDP is not a measure of "aggregate" value.
For example, if Jim's income is $4,000 and Janis's income is $1,000, does this mean that Jim's wants and needs are satisfied better than Janis's? We don't know. Likewise, if Jim tells you that, on a scale from one to five, his level of happiness is three, and Janis tells you that her level of happiness is four, this does not tell you that Jim is less happy than Janis — because Jim's level three and Janis's level three are not the same subjective state of mind.
Any comparison of subjective states requires the same frame of reference. Even if we know that one individual can buy more goods with his or her income than another, it does not follow that we may compare the two individuals' respective satisfaction. Not only do we not know what each person wants to buy, but even if we knew what each wanted to buy, we have no way of measuring how much satisfaction each one enjoyed in doing so. (This is one of the basic postulates of neoclassical economics, formally articulated by Carl Menger in his treatise Principles of Economics.)
The dubious nature of value measurements becomes even clearer when we note that many voluntary exchanges could never be included in the GDP. For example, friendship is a direct exchange of highly specific services that does not involve an exchange of money (and thus cannot be recorded or taxed in terms of money). However, the provision of friendship is a productive activity like any other. The service is provided to other people because they value the service in the same way they value eating apples or watching a movie. Yet who can tell us the aggregate value of friendship produced in Argentina in 1998?
Another, even more obvious example is this article. The exchange between its author and the Ludwig von Mises Institute did not involve any exchange of money, and it will not be recorded as a productive activity in either the Canadian or the US GDP. However, both parties benefited from the production and exchange of the article. (It is my hope that there is a third party that will benefit as well — the readers.)
If one adopts the position that the satisfaction of one's needs and wants is the ultimate purpose of human action, then the economic success of one's actions can only be measured by ascertaining the degree to which one's needs are satisfied. But, since satisfaction cannot be measured outside the frame of reference of the given individual, the success of one's actions cannot be evaluated by anyone other than the same person whose actions are being evaluated.