writer’s note: i need to collect my laundry now, so this blog post has not been grammatically debugged. bite me.
“Why did you get married? And why did you marry that person?” These are questions that economists and many scholars in various disciplines care about, all the time through history til now. They approach these questions from different perspectives, analyzing them using various statistical techniques and methodologies. While these questions are often addressed in the literature (at least according to the search results on Google Scholar), if you were to ask a specific married couple, whether they are happy or not, they would find it difficult to provide an instant, definite answer.
Above all these marriage questions, there’s a frequently mentioned notion called “assortative matching”. It’s a basic academic terms, which Britannica defines as:
Assortative mating, in human genetics, a form of nonrandom mating in which pair bonds are established on the basis of phenotype (observable characteristics). For example, a person may choose a mate according to religious, cultural, or ethnic preferences, professional interests, or physical traits.
Pause. It’s a little too tricky a definition. It is basically describing a phenomenon where married couples tend to be more similar to each other than to random individuals. But the term “more similar is quite vague. A better way to comprehend this concept is by considering a higher degree of similarity within a married couple compared to their feasible mating set. Wildly speaking, for all men $M$ and women $W$, denote $\text{sim}(m, w)$ for $\forall m\in M, w\in W$ as the “homogeneity rate” between them. In the context of assortative mating, a couple $(m, w)$ should exhibit a higher $\text{sim}(m, w)$ not only in comparison to global alternatives but also within their local feasible set of potential partners. This is because we optimize our choice of spouse for economic gains and emotional compatibility (maybe in an “online” flavour, for you usually can’t marry your ex-boy/girlfriend after breaking up with them). Nonetheless, mating itself is already nonrandom and confined to our local feasible set of choices. Therefore, ex-post-ly comparing the similarity rate between a marriage couple and their global average would be unfair. It makes more sense to restrict the comparison of “similarity” to the feasible set of potential mates.
Nevertheless, this phenomenon is real, people recognize it, with loads of economists trying to understand it… BUT every now and then we seem to be, actually, leaning towards this arrangement. So, instead of arguing over the casuality of assortative mating and its social welfare inequality implications, there would be more fun in studies that examine whether couples would be better off if they had a certain level of heterogeneity in their phenotypes. More ambitiously, it would be intriguing to investigate whether there exists an optimal pattern of similarity for couples, in terms of their happiness and welfare after marriage. Furthermore, can we find better measures of such heterogeneity than Shannon entropy? (Yeah Shannon entropy is a reliable metric, but please…anything more engaging, perhaps?) These questions can be explored from an individual perspective and beyond.
However, from a casual perspective, attempting to categorize or pinpoint the causes or effects of assortative matching can be a challenging task, especially when using economic methodology. Basic economic principles assume that people are rational to some extent and act as (general) utility maximizers when making decisions. However, as Shakespeare pointed out over six hundred years ago in “A Midsummer Night’s Dream”:
Love looks not with the eyes but with the mind, and therefore is winged Cupid painted blind.
Love and attraction often defy rationality, it’s difficult to apply strict economic principles to matters of the heart.