Suppose that apples sell for more than oranges and Parliament in it’s wisdom decides that, at last, apples and oranges must be compared. Not by shoppers — shoppers are biased, they merely reveal what they are willing to pay — but by a tribunal, which will determine whether apples and oranges are of truly equal value and thus must sell at the same price.

What would the tribunal need to know?

Start with land. Orange groves sit on Florida real estate with one set of alternative uses; apple orchards occupy Washington hillsides with another. The opportunity cost of an orange includes the housing development, the solar farm, the tourist attraction not built on that grove. How is the tribunal to value what was never built? Perhaps you answer: look at land prices. Brilliant suggestion, I reply. Keep going.

Next, capital. Orchards take years to mature, so today’s fruit embodies investments made under yesterday’s expectations about today, financed at interest rates the tribunal must somehow incorporate. Then storage: apples keep, oranges rot, so an apple and an orange in April are different goods than the “same” fruits in October. Add transportation, refrigeration, frost, pests, crop insurance, the option to divert fruit into juice, cider, marmalade, or pie, substitution with every other item in the produce aisle, and the shifting preferences of millions of consumers, each of whom knows things about his own breakfast that he could not articulate to a tribunal. It all matters.

To determine the “just” price of apples and oranges, the tribunal would need the entire general-equilibrium system.

Market prices are necessary to compare alternative uses of resources, as Mises taught us in 1920. In 1945, Hayek added the knowledge problem: the relevant knowledge is dispersed, local, tacit, and fleeting. Free markets are the only institution that aggregates that knowledge, articulates it in prices and gives people a reason to listen and respond. A price is a signal wrapped up in an incentive. Apples and oranges can be compared but only by the incomparably complex operations of the price system. There is a reason we call it the super-market.

Britain is now running this experiment in the labor market–Is a retail worker equal to a warehouse worker? A canteen worker equal to a coal miner? A dinner lady equal to a gravedigger?

Under the Equality Act’s “equal value” provisions, tribunals compare jobs by scoring their intrinsic properties — effort, skill, responsibility, working conditions — the labor theory of value applied to labor. How is it going? The Tesco litigation began in 2018; the tribunal’s fact-finding hearing ran 36 days, its judgments run to more than 900 pages resting on some 19,000 pages of training manuals, and the independent experts have yet to begin the report that will actually say whether a shelf-stacker’s job equals a warehouse worker’s. Eight years, and the calculation has not started. Apples and oranges, adjudicated but not, as Orwell or Marx or Stafford Beer might have imagined, by a industrial bureaucracy or by an all-knowing artificial intelligence but by lawyers and commissions and tribunals. The worst of all worlds.

And having discovered that the tribunal cannot price two jobs in a decade, the government now proposes to add race and disability comparisons and an enforcement unit to publish official guidance on which reasons for a wage difference are permissible. A bureau of allowable scarcities.

Moreover, let us say that one day the tribunal reaches its conclusion and finds the truly just apple to orange price. At last, nirvana. The next day the public learns that vitamin C really does combat cancer–the demand for orange juice skyrockets. To encourage more orange juice production we need a higher price but wait…nothing about oranges or apples or the labor required to produce them has changed. We need to attract more labor to the orange juice industry but the effort, skill, responsibility and working conditions of orange juice workers has not changed. How can we justly pay them more than their apple juice brethren? Blank out.

The market compares apples and oranges every day. It is the only institution that can. But there is a deeper error here than computation. Suppose the tribunal succeeded. Suppose that after another decade it delivered the true and final score, shelf-stacker versus warehouseman. What would it have found? Not justice. A wage is not a grade on your character or a measure of your worth as a human being. A wage is a price — a report on how scarce your skills are relative to the desires of people you will never meet. Nurses are not morally less worthy than plumbers should they earn less than plumbers or vice-versa, and no one thinks otherwise except the tribunals.

Hayek nailed it in The Mirage of Social Justice: justice is about conduct — how one person treats another. An employer who defrauds his workers, an employee who steals from the till, a product sold under false pretenses — condemn them, take them to court. But the pattern of prices that emerges from millions of voluntary trades is nobody’s conduct. No one chose it, no one designed it, no one can be guilty of it. The constellation of prices is, in Ferguson’s phrase, the result of human action but not of human design. Demanding that prices be just is a category error, like suing the weather. Prices don’t grade our merit; they guide our actions. Ask them to do the first and they can no longer do the second.

Judge Anthony Kennedy said it well in the Ninth Circuit ruling that (mostly) killed comparable worth in the US: “neither law nor logic deems the free market system a suspect enterprise.”