According to Wikipedia, an engagement ring is a ring indicating that the person wearing it is engaged to be married, especially in Western cultures. A ring is presented as an engagement gift by a partner to their prospective spouse when they propose marriage or directly after a marriage proposal is accepted.
Although the ancient Egyptians are sometimes credited with having invented the engagement ring, and the ancient Greeks with having adopted the tradition, the history of the engagement ring can only be reliably traced as far back as ancient Rome.
In the second century BC, the Roman bride-to-be was given two rings, a gold one which she wore in public, and one made of iron which she wore at home while attending to household duties. At one time Roman citizens wore rings made of iron. In later years senators who served as ambassadors were given gold seal rings for official use when abroad. Later the privilege of wearing gold rings was extended to other public officials, then to the knights, later to all freeborn, and finally under Justinian, to freedmen. For several centuries it was the custom for Romans to wear iron rings at home, gold rings in public. During this period a girl or woman might receive two engagement rings, one of iron and one of gold.
The first well-documented use of a diamond ring to signify engagement was by the Archduke Maximilian of Austria in the imperial court of Vienna in 1477, upon his betrothal to Mary of Burgundy. This then influenced those of higher social class and of significant wealth to give diamond rings to their loved ones.
In South Africa, diamonds were first found in 1866, although they were not identified as such until 1867. By 1872, the output of the diamond mines exceeded one million carats per year. As production increased, those of lesser means were able to join in on this movement. However, diamond engagement rings were for a long time seen as the domain of the nobility and aristocracy, and tradition often favored simpler engagement bands.
In the United States, the popularity of diamond engagement rings declined after World War I, even more so after the onset of the Great Depression.
In 1938, the diamond cartel De Beers began a marketing campaign that would have a major impact on engagement rings. During the Great Depression of the 1930s, the price of diamonds collapsed. At the same time, market research indicated that engagement rings were going out of style with the younger generation. Before World War II, only 10% of American engagement rings contained a diamond. While the first phase of the marketing campaign consisted of market research, the advertising phase began in 1939. One of the first elements of this campaign was to educate the public about the 4 Cs (cut, carats, color, and clarity). In 1947 the slogan “a diamond is forever” was introduced. Ultimately, the De Beers campaign sought to persuade the consumer that an engagement ring is indispensable, and that a diamond is the only acceptable stone for an engagement ring.
The idea that a man should spend a significant fraction of his annual income for an engagement ring originated from De Beers marketing materials in the mid-20th century in an effort to increase the sale of diamonds. In the 1930s, they suggested that a man should spend the equivalent of one month’s income in the engagement ring. In the 1980s, they suggested that he should spend two months’ income on it. In 2012, the average cost of an engagement ring in the US as reported by the industry was US$4,000. In a 2015 scholarly study, almost a quarter of couples said that they did not buy a ring, and another third spent less than US $2000 on it. Less than 15% of couples spent $4,000 or more. In the UK, estimates of the average cost of an engagement ring range from £1200 to £2000. Scholarly research indicates that expensive engagement rings are associated with early divorces, possibly because spending more than US$2,000 on an engagement ring is strongly associated with debt-related stress. Couples that spend less money on engagement rings and the wedding ceremony tend to have longer marriages and a lower risk of divorce.