One half of all marriages ends in divorce This frequently uttered factoid looks like a good reason to save money on an expensive wedding. But can it be true? Statistics New Zealand’s Population Statistics unit records the number of marriages registered each year and tracks how many of these end in divorce. Analysis of this data shows that roughly one-third of couples who married in 1970 had divorced by their jade wedding anniversary (35 years). This suggests that two-thirds of marriages end in the death of one partner. But aren't divorce rates increasing? Of those who married in 1980, one-third of couples had already divorced by their silver wedding anniversary (25 years). This is still well below one-half of all marriages. The longest marriage certified by the Guinness Book of Records is 86 years, although there are longer marriages pending verification. Conclusion This myth is busted. How did this myth arise? There are roughly 10,000 divorces and 20,000 marriages in NZ each year. 10,000/20,000 = 1/2 – so one-half of all marriages end in divorce, right? Wrong! The couples divorcing in a year are not the same couples who marry in that year, but a subset of all those who married in preceding years and have not yet divorced (a much greater number than 20,000). When measuring the frequency of an event in a population (eg divorces) it is important to express the number of events in the context of the population who are likely to experience that event (sometimes called the 'at risk' population). For divorces, that population is the estimated number of existing marriages (from all years past and present). The method used to bust this myth, where divorces are analysed by year of marriage, is known as a ‘cohort analysis’.
What the chart above actually shows is the divorce to marriage ratio. Based on that NZ would be 43% in 2015, or the same colour as the UK.
Lindsay Mitchell has been researching and commenting on welfare since 2001. Many of her articles have been published in mainstream media and she has appeared on radio,tv and before select committees discussing issues relating to welfare. Lindsay is also an artist who works under commission and exhibits at Wellington, New Zealand, galleries.