Last Updated: April 2026
TL;DR:
- De Beers Group’s ad agency, N.W. Ayer & Son, created “A Diamond Is Forever” in 1947 — copywriter Frances Gerety wrote the actual line.
- Before the campaign, only about 10% of U.S. engagement rings carried a diamond. By the early 1980s that number topped 80%.
- De Beers once controlled roughly 85% of the world’s rough diamond supply. In 2026 that figure sits closer to 35%, and Anglo American is in the final stages of selling its 85% stake in the company entirely.
Every jeweler I know has sold a ring on the strength of four words: A Diamond Is Forever. If you’ve ever wondered why diamonds are so expensive in the first place, the answer starts with this slogan. It wasn’t discovered in a boardroom of diamond executives — it came from a copywriter working late on a deadline in 1947. This piece breaks down exactly who wrote it, why De Beers needed it, and where the diamond monopoly that built stands in 2026.
Which Company Coined the Ad Slogan “A Diamond Is Forever”?
De Beers Group commissioned the slogan, and its advertising agency, N.W. Ayer & Son, produced it in 1947. The line was written by staff copywriter Frances Gerety at the agency’s Philadelphia office. De Beers has run it in every engagement ad since 1948 — a 78-year unbroken streak for one tagline.
De Beers wasn’t selling a rare stone at the time. Diamonds had flooded the market since large deposits were found in South Africa around 1870, and prices were sliding. According to Sotheby’s, De Beers needed American consumers to see diamonds not as a commodity but as a permanent, non-resellable symbol — which conveniently also meant buyers would never flood the resale market and depress prices further.
Who Was Frances Gerety, the Copywriter Behind It?
Frances Gerety was a staff copywriter at N.W. Ayer & Son who wrote “A Diamond Is Forever” for a 1947 De Beers pitch. She never married. The line was reportedly one of several she jotted down before bed and almost got cut by her own colleagues, who didn’t think it was strong enough.
Per Wikipedia’s Gerety entry, she spent over 25 years on the De Beers account and is credited with inventing the modern engagement-ring script — the idea that a diamond should be a man’s biggest and most permanent purchase before marriage. In 1999, Advertising Age named it the top advertising slogan of the entire 20th century, beating out lines for Coca-Cola and Nike.
Why De Beers Needed a New Slogan in 1947
The Great Depression had gutted diamond sales, and by the mid-1940s the company was staring at a stone nobody urgently wanted. Diamonds were not rare in supply — they were rare only in how they were marketed. N.W. Ayer’s job was to reframe the purchase decision entirely: don’t buy a diamond because it’s scarce, buy it because breaking up a marriage to sell it back would feel like betrayal.
That reframing worked because it attacked resale directly. If you’ve read our breakdown of why diamond resale value stays so low, you already know the psychology stuck — most buyers today still treat a diamond as a keepsake, not an asset, exactly as the 1947 campaign intended.
How Did the Slogan Change the Engagement Ring Market?
Before 1947, roughly 10% of American engagement rings contained a diamond. By the early 1980s, that share had climbed past 80%. Between 1939 and 1979, De Beers’ U.S. wholesale diamond sales grew from $23 million to $2.1 billion — a nearly 90-fold increase tied directly to this one campaign.
According to The Drum, the ad agency didn’t just sell diamonds — it invented the modern engagement ring as a cultural expectation. Movie stars were loaned diamonds to wear on screen, magazine editorial content quietly featured De Beers stones, and etiquette columns began treating a diamond ring as a prerequisite for a “proper” proposal.
The 1977 “Two Months’ Salary” Campaign
Thirty years after the original slogan, De Beers ran a black-and-white spot set in wealthy enclaves like Cape Cod and the Hamptons. The only color on screen was the gold-toned diamond solitaire. The male lead explained that the only way his two months’ salary could “last forever” was to spend it on a diamond.
That single ad line — “two months’ salary” — became an unofficial spending benchmark for decades of grooms, even though it had zero basis in economics. It was pure copywriting, and it worked because it gave buyers a number to anchor against instead of a range they had to guess at themselves.
What Is the De Beers Group?
De Beers Group is a diamond company handling exploration, mining, grading, and sales, with roughly 20,000 employees across Botswana, Namibia, South Africa, and Canada. It owns retail brands including De Beers Jewellers, Forevermark, and Liberté by Forevermark, and it still operates as a partner jeweler in dozens of markets worldwide.
The company doesn’t just mine rough stone — it runs the full pipeline from ground to display case. That vertical control is exactly what let one slogan reshape an entire industry’s buying habits for three generations.
How De Beers Built (and Lost) Its Diamond Monopoly
Cecil Rhodes founded De Beers Consolidated Mines in 1888 after buying up South African claims one by one. At his peak, Rhodes’ company controlled more than 85% of the world’s diamonds. He created the Diamond Trading Company (DTC) as a gatekeeper — only pre-approved “sightholders” could buy rough stone, and De Beers set the price by stockpiling supply when demand was weak and releasing it when demand spiked.
That control held for roughly a century. It cracked when new mines opened in Canada, Russia, and Australia — most notably Argyle — and started selling directly to cutters without going through De Beers’ distribution channel. Once competitors could market their own stones the same way De Beers had taught the world to want them, the monopoly had no real defense left.
What Is De Beers’ Market Share in 2026?
De Beers holds roughly 35% of the global rough diamond market in 2026, down from a peak of about 85% in the mid-20th century. The drop came from Canadian, Russian, and Australian mines selling independently rather than through De Beers’ old Diamond Trading Company channel.
If you’re comparing diamonds against other stores of value, this loss of pricing control is a big reason. Our piece on the resale value of diamond vs. gold covers why a market that no longer controls supply also struggles to control resale price.
Where Is De Beers Headquartered?
De Beers Group is headquartered in London, United Kingdom. Its sightholder sales and rough-diamond distribution operations are also run out of Botswana, where the government is a co-owner and the company operates major mining joint ventures.
Who Owns De Beers Today?
As of 2026, Anglo American owns 85% of De Beers and the Government of Botswana owns the remaining 15% — but that’s changing fast. Anglo American has confirmed it’s in the final stages of selling its stake, reportedly valued near $1 billion, as part of a broader move to focus on copper and iron ore.
According to JCK Online, Anglo’s CEO has said the company hopes to close the sale before the end of 2026, with reported deal structures around $750 million upfront plus a further $250 million tied to performance. Whoever buys the stake inherits the brand behind the most successful ad slogan in history — but not the pricing power that once came with it.
The Bottom Line
De Beers coined “A Diamond Is Forever” in 1947 to solve a sales problem, and Frances Gerety’s four words did more for diamond demand than any mine ever could. The slogan turned a slow-selling stone into a marriage requirement and pushed diamond engagement rings from 10% to over 80% of the U.S. market in a few decades. But the monopoly that funded the campaign is gone — De Beers’ market share has fallen from 85% to about 35%, and its current owner is trying to sell out entirely. If you’re shopping for a diamond today, know that the “rarity” behind the price tag was manufactured copy, not geology. Check out our guide on why some diamonds carry little resale value before you commit two months’ salary to one.
Frequently Asked Questions
Did De Beers really invent the phrase, or did an outside agency write it?
De Beers commissioned the campaign, but the actual four words were written by Frances Gerety, a staff copywriter at N.W. Ayer & Son, De Beers’ Philadelphia-based ad agency. De Beers owns the slogan and has used it continuously since 1948, but the company itself didn’t write the line — its hired agency did.
Are diamonds actually rare?
No. Large diamond deposits have been mined since the 1870s, and De Beers’ own historical strategy depended on stockpiling supply to create artificial scarcity rather than natural scarcity. Colored and flawless diamonds are genuinely rarer than standard white diamonds, but the everyday stone in most engagement rings is not scarce in the way the marketing implies.
Why did diamond engagement rings become standard after 1947?
The “A Diamond Is Forever” campaign linked diamonds to permanence and love at the exact moment postwar prosperity gave young couples more money to spend. Movie placements, magazine tie-ins, and a benchmark spending figure (later “two months’ salary”) gave an entire generation a script to follow, and diamond ring adoption jumped from about 10% to over 80% within a few decades.
Does De Beers still control diamond prices?
Not the way it used to. De Beers’ market share has fallen to roughly 35% as Canadian, Russian, and Australian producers built their own sales channels outside De Beers’ old Diamond Trading Company system. The company still influences branding and grading standards, but it no longer sets a single global price the way it did through most of the 20th century.
Who owns De Beers now, and is that changing?
Anglo American currently owns 85% of De Beers, with the Botswana government holding the remaining 15%. Anglo American is in the final stages of selling its stake, reportedly near a $1 billion valuation, as part of a broader plan to exit diamonds and focus on copper and iron ore mining.
Stephanie is a jewelry lover when she was a teenager. Her major was fashion design when she was in college. She is a jewelry designer at SOQ Jewelry and other design companies. Now she is also a writer for our website. She writes a lot of designs&brands posts with very actionable tips.