AT FIRST sight, the master-servant relationship seems based on economic differences: a mutually beneficial transaction between one party with more money than time (or willingness) to perform household tasks and another in the opposite situation. And indeed many of the world's 50m-100m domestic workers are migrants propelled across borders by gulfs in wealth as great as those between aristocratic Victorians and their maids, or colonial Portuguese in Brazil and their slaves.

But differences in financial status are not all that drives the maid trade. Bridget Anderson of Oxford University's Centre on Migration, Policy and Society has interviewed employers of domestic staff in a number of rich countries, and found that many prefer immigrants to locals because “it lets them talk about the wonderful things [the maid] is doing with her money back home”, thus portraying a dead-end job as a golden opportunity.

Inequality is part of what employers are buying. Simel Esim and Monica Smith of the International Labour Organisation studied domestic workers in the United Arab Emirates, and concluded that servants were there in part to raise their mistresses' status by slotting into the household below them. Some Brazilians employ only black maids, says dark-skinned Alzira—“because that's who is a maid, that's why. Some women don't want a maid they think could be as nice looking and well turned out as themselves, who could compete with them.”

Employing people you look down on may be a cheap way to feel better about yourself. But letting them look after your home and children requires uncomfortable mental contortions. These are skewered in “The Help”, a novel set in 1960s Mississippi which has recently been turned into a film. The villain tries to force white households to provide black maids with separate bathrooms because, conveniently for those they cook and clean for, “99% of all colored diseases are carried in the urine.”

In “The Theory of the Leisure Class”, Thorstein Veblen looked at many seemingly puzzling features of the master-servant relationship: the effort of managing them; the elaborate uniforms they were required to wear inside private homes; the sadly frequent abuse. He pointed out that, even in 1899, labour-saving devices would considerably reduce the need for household labour, which suggested to him that people hired servants not to relieve themselves of tedious tasks, but to be provided with “conspicuous subservience”. A servant both satisfied the master's “propensity for dominance” and presented a public “performance of leisure”. The liveried footman, who demonstrated by his decorative uselessness his master's ability to consume a great deal of unproductive labour, was the ultimate status symbol.

Prosperous and busy people employ nannies and cleaners to make life easy for themselves. But sometimes the point of having a servant is simply to be a master.