A very quick primer on why income and prices (GDP) is a measure of well-being

There is a common misconception (sometimes even deliberate misdirection) that GDP is distinct from well-being. You hear phrases like "we need to abandon GDP and move to well-being instead". This is erroneous. GDP is an indicator of well-being. One with a lot of attractive properties. The income and price data that are used to build GDP are similar indicators. In this post I want to explain how income, prices, and GDP work as indicators of well-being in an accessible manner (i.e. very little math).


I should preface this by saying that I am keen to move gradually over the next century away from income and towards some more holistic way of thinking about well-being and progress. However, there are major dangers associated with rushing towards happiness and subjective well-being specifically, notably paternalism, technocratic conceit, perverse distributional consequences from adaptation, major measurement error, etc. I write about these in my academic works and will provide explainers as those longer papers become publicly available. Some discussion is available here: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3223959

There are four big reasons why GDP is a good indicator of well-being: it is objective, inter-personally cardinal, unidimensional, and liberal. I will take them one-by-one.


Objective

Measuring and debating something is a lot easier if it is observable independently of personal judgement. Income is objective, happiness is not. Now I must immediately note that measuring income is not straightforward, especially when you’re dealing with poor and/or vulnerable people. People don’t remember their incomes accurately, don’t account for transfer payments, forget gifts, overstate their tax bill etc. Things are similarly complicated at the other end of the scale when you’re trying to aggregate economic activity across the entire economy into GDP. Measuring happiness and well-being is an order of magnitude more difficult, but it should not be assumed that measuring income is straightforward. The important thing, in any case, is that income, prices, and GDP are all observable. An analyst can engage with them without asking anyone for a subjective judgement. This is very important in the context of public policy because it means you have a fact that is perceived similarly by all stakeholders. I think this is a weak argument for the most part, because subjective well-being scores, once collected, are observed the same way by all parties. Sure, they can be manipulated—you could do the survey on a sunny day in spring if you wanted higher scores—but so can income measures.


Cardinality  

Cardinality is about how things are in proportion to one another. For example, $2 is twice as large as $1 and 4 times as large as $0.50. In contrast, ordinal relationships are simply about rank, like biggest to smallest or some such, with no regard for proportion. For example, 2 > 1 > 0.5. Cardinal vs ordinal is extremely important in the context of interpersonal welfare comparisons. Think about the justice of a distribution for a moment. In one society you have people Say you’ve got 5 people with incomes of 100, 50, 50, 20, 20, 20, 20, 10, 10, and 10. You want to make this society more equal. It matters that the person with 100 income is not only rank #1 but also has 10 times as much income as the people ranked #8–#10. You can do such cardinal comparisons with income. I don’t want to go into the details in this post, but subjective well-being metrics do not produce cardinal measures of well-being. I don’t even think they produce ordinal measures of well-being, which is a huge problem, but assuming that they did, we would still have reason to maintain some interest in income.


Unidimensional

When you’re trying to compare one person’s welfare with other another, it helps if your indicator of welfare has only a single dimension (i.e. unidimensional). The human development index, millennium development goals, sustainable development goals, and other attempts to move beyond GDP in the objective indicators space have all struggled with dimensionality. Imagine you have two people, both 40 years old. One has perfect health, an income of $25 000 p.a., and lives in an ugly, crime-ridden neighborhood. The other lives in a beautiful, safe neighborhood on an income of $140 000 p.a., but has a bad knee and shoulder that prevents them from doing just about any form of exercise other than walking, and even that is a little uncomfortable. Which one of these people is better off?

The answer is that it depends on what you value. Maybe you don’t care so much that you’re immobile because your passion is crafting model trains and for that income is critical. Or maybe you care loads about living in nature and you would be willing to take an enormous pay cut for that. How can we compare people in a way that takes account of these differences in preferences?

Prices to the rescue! People communicate their preferences into markets through their consumer demand. They are willing to pay more for things they have a stronger preference for. Producers look to make profits by providing things people want at least cost. This is the supply side. The interaction of demand and supply gives rise to market prices, which reflect the cost and benefit of a good relative to all other goods. Prices are measured in money which is unidimensional and inter-personally cardinal i.e. a dollar is worth the same to two average Americans even though they will spend it on different things. In this way, income and prices provide us with a means of conducting unidimensional, inter-personally cardinal welfare comparisons. This is critical for thinking about justice, but also for doing relatively simple cost-benefit calculations for things like building a new light rail network versus expanding the existing bus network.   


Liberal

People spend money (and health, education, and rights) on whatever they have the strongest preference for. It is a very slippery slope to dystopia when governments start to assume that they know better than individual citizens what the preferences of those citizens are. This is one of the foundational principles of liberalism, crisply articulated in the harm principle—governments only have a right to interfere with a sovereign individual if that individual is doing harm to someone else. It is a relatively uncontroversial thing for governments to expand the options available to people: help them achieve greater wealth, education, health, and political enfranchisement. People will choose from among the growing number of possibilities available to them which live they would most like to lead.

This or an even more limited role for government is implicit in most political theory since the enlightenment. You have to go all the way back to Plato to find someone advocating that government, in all its wisdom, choose the kind of life someone should live on the grounds that this life will make them happiest. And yet it is precisely this transformation in the role of government that is implicit in a lot of contemporary advocacy for policy to target happiness and subjective well-being (SWB). For example, a recent paper argued for greater progressivity of taxation on the grounds that it makes poor people happier and rich people not so unhappy. Leaving aside the abysmal treatment of causation in the paper, this attitude rides roughshod over the last 400 or so years of political theory. In particular, it rides over social contract issues around the legitimacy of taxation enforced by state power. The potential to violate liberal norms in the quest to maximise happiness should be clear as day here. I am not at all a libertarian and still find the naivety of such policy advocacy staggering.  

It is worth mentioning is this context that advocates of subjective well-being policy frequently claim that life satisfaction scales are a “democratic” metric. For example, Clark et al (2019, p. 4) write that: “Third, and most important, [life satisfaction] is democratic—it allows individuals to assess their lives on the basis of whatever they consider important to themselves”. Similarly, Frijters et al (2019) write that life satisfaction scales “takes individuals seriously as political agents and sets them at the top of the judgement tree”.


This claim strikes me as specious for two reasons. First, because respondents are never asked why they hold a level of life satisfaction. Instead, their responses are placed on the left-hand side of a regression and then variables chosen by analysts are used to determine what causes respondents’ levels of satisfaction. Indeed, SWB scholars emphasise that respondents cannot be asked what determines their satisfaction because this would contaminate their responses with present, social desirability, and other biases. It seems that in practice, life satisfaction scales decidedly do not take individuals seriously as political agents. Second, because there is at present no process by which respondents assent to how their responses are translated into policy proposals. Democracy is fundamentally about making decisions by vote. Arguing, for example, that such and such a program should be prioritised in government budgeting because some technocrat has observed that it is associated with higher SWB than some other policy involves no voting. One could argue that scales are liberal because they respect the individual’s own judgement about their life. However, advocates must then explain why they are superior in this regard to the status quo in which governments merely act to maximise citizen’s capabilities and then leave them to decide how to leverage those resources. The advantage of the prevailing paradigm, namely preference-satisfaction measured using income and prices, is precisely its liberalism. 

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