Is the divorce rate declining?

On Tuesday, April 30, the CBC published an article claiming that the rate of divorce in Canada is declining, and contrasting that hard data with the common misconception that half of marriages end in divorce. The article is a summary of a recent report published by the Vanier Institute on the Family, which is itself drawn from data published by Statistics Canada (references therein).

The CBC article embeds the above chart, created with the ever-cromulent DataWrapper. The punchline of the chart is pretty clear: the divorce rate in Canada peaked in 1987 (the chart points out that the Divorce Act was amended in 1986). Since then, the divorce rate has been declining in lock step with the declining marriage rate. Both rates plummeted in 2020 for obvious reasons, which is the last year for which we have available data.

While neither the CBC article nor the Vanier institute are factually incorrect, it isn't apparent to me that these data have anything whatsoever to do with divorce. If fewer people are married overall, then we would expect a lower rate of divorce. Even analyzing the rate of divorce as a percentage of Canadians who are married doesn't tell us all that much, because an increasingly large share of the population are older people who are less likely to divorce at all (see below).

Fortunately, Statistics Canada tracks the yearly divorce rate broken up by the year in which the couple was first wed. We can use this to track a "marriage survivorship curve". This isn't a true survivorship curve, because is doesn't tell us how many of these marriages are still intact (the alternative way a marriage can end isn't represented), but rather the cumulative likelihood that the marriage resulted in divorce as a function of time.

The following chart shows the divorce rate as a function of years of marriage for a couple married in 1971 (the earliest year for which data are available). The slider allows you to change to view couples married in later years, but we have less and less data for more recently married couples as we don't know the eventual fate of younger marriages.

The basic shape of this curve shouldn't come as a surprise. Newlyweds rarely divorce, but a rapid acceleration is underway by the end of the first decade. This has begun to level off by the end of the second decade. For couples married in 1971, the curve has almost fully leveled out by the time the couple has been married for 30 years (partly because they've made it that far, partly because one member of the couple has died, making it impossible for the marriage to result in divorce at that point).

As we examine couples married later than 1971, the curve pulls up and to the left. More marriages result in divorce, and a greater percentage of couples are divorced earlier in their marriages. As we get to younger couples, this trend may be leveling out or even reversing; however, it's difficult to know for sure given the relatively short timespan we have to work with: these young couples simply aren't yet through the years when divorce is most likely to occur.

To think of this slightly differently: let's ask how long it is until some fraction of married couples are divorced. The "half-life" of divorce is technically infinite, because it is not true and has never been true that half of marriages end in divorce (the curve never reaches 500 out of 1000 marriages). However, the period right around 140 out of 1000 is quite dynamic. How long does it take for 14% of couples to get divorced?

Note: click on the left-hand graph above to change the examined rate. Again, higher rates mean we have less data to work with!

This shows approximately the same thing. A big drop the expected shelf-life of a marriage occurred throughout the 1970s. Also, the "leveling-out" point of all these curves is higher, so a greater percentage of couples overall are divorced. The drop-off was pretty much done by the time the 80s were underway: a couple married in 1981 has approximately the same "divorce curve" as a couple married in 2001.

This trend may have rebound in recent years: for couples married around 2011, the curve seems a little wonky and may be accelerating more slowly than for couples married in the 80s, 90s, or noughts. Someone with different skills than me could probably use this to tell a story about the Great Recession or the cost of housing in Canada. It is worth saying again that 2020 is the last year for which we have available data: a couple married in 2011 was right in the divorce sweet spot when the pandemic hit. Time will tell whether the declining rate is a trend that will continue.

Conclusion

The CBC (and Vanier Institute) reports on the declining divorce rate are interesting, but are not about divorce. Couples are most likely to divorce in their first 20 years or so of marriage. They became somewhat more likely to do so the later in the 1970s they were married; a trend that has been stable ever since then. The fact that a Canadian in 2020 is relatively unlikely to divorce is primarily because that Canadian is: (1) less likely to be married in the first place, and (2) if they are married, likely to have been married for a relatively long time.