“A diamond is forever” was the slogan that made diamonds the most sought after object in North America in the late 1920s, around the time when it was entering a depression and diamond prices were falling.

Advertising made the diamond trade soar by doing one thing essentially: suggesting to young American men that if it was really love they were after, then one month’s salary spent on a diamond was the best way to prove it. It worked.
The growing diamond empire suddenly boomed. The true knack of advertising laid in the fact that something with really no lasting value – a diamond – was suddenly being equated to something invaluable – romantic love.
Some cultures have myths surrounding diamond rings. Advertising myths, however, are created just so the diamond business can be propped up. Ruthless advertising and marketing of diamond rings end up creating an artificial need for an article of such little value as a diamond ring, ultimately.