How many marriages are there per year?

Answer 1

Considering the multitude of different cultures on earth, the exact answer depends on what you recognise as marriage. Do you count group marriages? What about same-sex marriages? Requiring a marriage to be sealed in a temple of the Latter Day Saints will likely result in a very trustworthy number, while accepting common-law marriages will involve quite a bit guesswork. For even more guesswork count in the temporary marriages allowed in Shia Islam (see Nikah mut'ah).

A Fermi calculation can give reliable upper bound of marriages between two people, Ideally, a human being marries once in a lifetime. While there are people who remarry (sometimes more than once), there are also those who never marry; both groups together probably have the ideal number of marriages per life, i.e. one. Wikipedia states 67.2 as the 2010 world average of life expectancy, so a human being marries once every 67.2 years.

Currently there are about 7 * 10^9 people living on earth, which means 3.5 * 10^9 marriages. Distributed over 67.2 years we have about 52 * 10^6 marriages per year. (For those not familiar with scientific notation, 10^6 is a million, and 10^9 is a milliard or a billion, depending on whether the long or the short scale is used. Scientific notation neatly avoids the ambiguity of billion)

For the yearly number of marriages in a particular region, simply follow the same pattern: Divide half the population by the life expectancy. For example, in 2005 Germany had 82.5 million people and a life expectancy of 79.48 years. The resulting number of 518998 is noticeably higher than the recorded number of 388451 marriages in that year, but an acceptable ballpark figure. (All data from Wolfram Alpha.)