The three-month-salary rule comes from a 1930s marketing campaign. De Beers, a leading diamond cartel that controlled 60% of all rough diamond output at the time, was looking for a way to drum up sales. The Great Depression had caused an obvious drop in diamond sales, so De Beers began what would become one of the most successful marketing campaigns of all time by accomplishing two things: tying a person’s income to engagement ring prices and linking diamonds to engagement rings.
Even though the catchphrase “A Diamond Is Forever” still persists today, you might be interested to know that before this De Beer’s marketing campaign, only about 10% of engagement rings even contained diamonds. They were certainly not seen as the pinnacle of engagement ring stones the way they generally are today. It’s also important to realize that, in the United States, the original De Beers campaign promoted the idea that a single month’s salary was the correct amount of one’s income to spend on an engagement ring. This amount proved a person’s devotion and served as a way to quantifiably put a price tag on love.
However, De Beers also very successfully launched this campaign in Japan, where diamond engagement rings were entirely unheard of before WWII. And, unlike the more modest U.S. price tag, in Japan, the suggested price tag was three months of one’s income. The U.S. campaign shifted to a two-month-salary price tag in the 1980s and has continued increasing in recent years alongside inflation.