The “tradition” of spending several months salary on an engagement ring was a marketing campaign created by De Beers in the 1930’s. Before WWII, only 10% of engagement rings contained diamonds. By the end of the 20th Century, 80% did.
The idea was embedded in popular culture in the West by an advertising drive from the De Beers diamond cartel that started in the lean years of the 1930s. The Depression was a disaster for De Beers, which controlled 60% of rough diamond output. De Beers embarked on what it now describes as a “substantial” campaign, linking diamonds with engagement.
Prior to the 1930s, presenting a woman with a diamond engagement ring was not the norm. Even on the eve of World War Two, a mere 10% of engagement rings contained diamonds. By the end of the 20th Century, 80% did.