De Beers turned diamonds into an engagement must-have

By the late 1930s De Beers already controlled the great majority of the world's rough diamond supply, but supply control alone wasn't generating sales: the Depression had crushed luxury spending, and diamonds were seen as an extravagance mainly bought by the wealthy — only about 10% of American engagement rings contained one, with pearls and colored stones just as common. Restricting the flow of stones onto the market did nothing to fix a problem on the demand side.

The obvious lever, spending more on ordinary product advertising, assumes customers already want the category and just need to be nudged toward a brand; De Beers didn't have that problem solved yet. In 1938 it hired the ad agency N.W. Ayer with a different brief: not to sell De Beers diamonds over a competitor's, but to make the American public believe an engagement without a diamond was somehow incomplete.

W. Ayer built a campaign around cultural engineering rather than product features — placing diamonds in Hollywood films as the object a suitor presents at the moment of proposal, running a 'Great Artists' series painted by the likes of Salvador Dalí and Picasso to attach diamonds to sophistication, and setting an unwritten price rule (spend a month's salary, later revised upward) that gave buyers a concrete, socially enforced benchmark instead of a vague sense of what to spend.

Manufactured an obligation: placed diamonds in films at proposals, set a spending benchmark, and coined 'A Diamond Is Forever' to suppress resale, making luxury a ritual.

Scarcity only works if people want the product; De Beers had to create that want.

Film placements and art attached diamonds to romance and sophistication, making them aspirational.

The month's-salary rule gave a concrete, socially enforced spending benchmark.

'A Diamond Is Forever' discouraged resale, suppressing the secondary market.

The manufactured obligation scaled with cultural adoption, not with scarcity.

When you control supply of a good people don't need, scarcity fails once demand stalls; manufacture an obligation that makes the purchase feel necessary.

By 1951 jewelers were telling Ayer that 'a girl is not engaged unless she has a diamond engagement ring'; diamond engagement-ring adoption climbed from roughly 10% of American engagements before the campaign to around 80% by the end of the century, and De Beers's annual diamond sales grew from about $23 million in 1939 to more than $2.1 billion by 1979.