The problem De Beers needed to solve in 1938
In 1938, De Beers approached N.W. Ayer & Son with a specific problem: American diamond sales had fallen sharply during the Depression, and the practice of giving a diamond ring as an engagement gift was largely confined to the wealthy. Working-class and middle-class Americans had engagement rings, but they were typically gold bands, possibly set with other gems. Diamonds were not the default. De Beers wanted to change this (Epstein, E.J., 1982, "Have You Ever Tried to Sell a Diamond?," The Atlantic Monthly, February 1982; Ayer account records as documented in various marketing histories).
N.W. Ayer's research identified that the obstacle was not desire, women wanted diamond engagement rings, but perceived necessity. Men did not feel they needed to buy a diamond; alternatives were acceptable. The campaign's strategic objective was to make diamond engagement rings not just desirable but necessary, to make a man who did not buy a diamond engagement ring feel he had failed in his romantic duty (Ayer research findings as documented in Epstein, 1982, op. cit.).
The campaign mechanics: celebrities, film, and the two-month rule
The Ayer campaign operated through multiple channels simultaneously. Celebrity engagement announcements in the press were leveraged to publicise diamond rings; photographs of celebrities and socialites wearing diamond engagement rings appeared in magazines; fashion editors were supplied with diamond ring imagery for their pages. Films, particularly romantic films, were approached about featuring diamond engagement rings in proposals and wedding scenes (Epstein, 1982, op. cit.; advertising history documentation).
The campaign also invented and disseminated specific rules about diamond engagement ring purchase, most notably the "two months' salary" guideline, which established a socially expected spending level for the ring. This guideline had no historical precedent; it was a De Beers marketing invention that became a widely accepted social norm (advertising history documentation; Epstein, 1982, op. cit.).
The slogan: "A Diamond Is Forever" (1948)
The genius of "A Diamond Is Forever" was in what it implicitly communicated about resale. A diamond that is forever is a diamond you never sell, it is an eternal gift of love, not a financial instrument. This emotional framing did two things simultaneously: it made the diamond purchase feel more significant (you are not buying a commodity; you are buying forever) and it prevented the development of a functioning secondhand diamond market that would undermine the value of new diamonds. If diamonds are forever, passed from generation to generation as symbols of eternal love, they are not resold. The absence of a resale market supported diamond prices (Epstein, 1982, op. cit.; analysis of "Diamond Is Forever" marketing strategy).
The Japan market: creating a tradition from nothing
The clearest demonstration of the campaign's power is Japan. In 1967, Japan had essentially no diamond engagement ring tradition. De Beers and N.W. Ayer ran a version of the diamond engagement ring campaign in Japan from the late 1960s. By 1981, approximately 60 percent of Japanese brides wore diamond engagement rings. A tradition that did not exist in 1967 had become a national norm in 14 years (Epstein, 1982, op. cit.; De Beers Japan market data).
Primary sources
Epstein, E.J. (1982). "Have You Ever Tried to Sell a Diamond?" The Atlantic Monthly, February 1982. [The definitive investigative account of the De Beers-Ayer campaign. Frances Gerety, the 1938 problem, celebrity strategy, "two months salary" invention, Japan market success, diamond resale market suppression analysis.]
Advertising Age, "Advertising Century: Top 10 Slogans" (1999). Advertising Age. ["A Diamond Is Forever" named advertising slogan of the 20th century. Frances Gerety attribution confirmed.]
De Beers Group historical records. debeersgroup.com. ["A Diamond Is Forever" used in every De Beers advertisement since 1948; campaign origin documentation.]