tl;dr micromarriages aren't fully analogous to micromorts, which makes it tricky to define them satisfactorily. I introduce an alternative unit: QAWYs (Quality-Adjusted Wife Years), where 1 QAWY is an additional year of happy marriage.

I once compiled a list of concepts which I’d discovered were less well-defined than I originally thought. I’m sad to say that I now have to add Chris Olah’s micromarriages to the list. In his words: “Micromarriages are essentially micromorts, but for marriage instead of death. A micromarriage is a one in a million chance that an action will lead to you getting married, relative to your default policy.”

It’s a fun idea, and helpful in making small probabilities feel more compelling. But upon thinking about it more, I’ve realised that the analogy doesn’t quite work. The key difference is that micromorts are a measure of acute risk - i.e. immediate death. For activities like skydiving, this is the main thing to worry about, so it’s a pretty good metric. But most actions we’d like to measure using micromarriages (going to a party, say, or working out more) won’t lead you to get married immediately - instead they flow through to affect marriages that might happen at some later point.

So how can we measure the extent to which an action affects your future marriages, even in theory? One option is to track how it changes the likelihood you’ll get married eventually. But this is pretty unhelpful. By analogy, if micromorts measured an action’s effect on the probability that you’d die eventually, then all actions would have almost zero micromorts (with the possible exception of some life-extension and existential risk work during the last few decades). Similarly, under this definition the micromarriages you gain from starting a new relationship (or even from literally getting married) could be mostly cancelled out by the fact that this relationship cuts off other potential relationships.

An alternative is to measure actions not by how much they change the probability that you’ll get married eventually, but by how much you expect them to causally contribute to an eventual marriage. The problem there is that many actions can causally contribute to a marriage (meeting someone, asking them out, proposing, etc) and there’s no principled way of splitting the credit between them. I won’t go into the details here, but the basic problem is the same as one which arises when trying to allocate credit to multiple contributors to a charitable intervention. E.g. if three different funders are all necessary for getting a project off the ground, in some sense they can all say that they “caused” the project to happen, but that would end up triple-counting their total impact. (In this case, we can use Shapley values to allocate credit - but the boundaries between different “actions” are much more arbitrary than the boundaries between different “agents”, making it harder to apply Shapley values to the micromarriage case. Should we count the action “skipping meeting someone else” as a contributor to the marriage? Or the action “turning your head to catch sight of them”? This is basically a rabbit-hole without end - and that’s not even getting into issues of marriage identity across possible worlds.)^[1]

Fortunately, however, there’s another approach which does work. When thinking about mortality, the medical establishment doesn’t just measure acute risks, but also another category of risk: chronic risks, like smoking. When smoking, you don’t get a binary outcome after each cigarette, but rather a continual degradation of health. So chronic risks are instead measured in terms of the expected decrease in your lifespan - for example, with units of microlives, where one microlife is one millionth of an adult lifespan (about half an hour); or with quality-adjusted life years (QALYs), to adjust for ill health and disability.

Analogously, then, the most straightforward metric for guiding our romantic choices is the expected increase in the time you’ll spend married - which we could measure in microwives (where one microwife is an additional half-hour of marriage). But I don’t think this is the best unit, because most people could accumulate many more microwives by dropping their standards, even if that’ll lead to unhappy marriages. So it’s important to adjust for how good we expect the marriage to be! My proposed unit: quality-adjusted wife years (QAWYs). Note that these are gender-neutral: QAWYs can involve either being a wife or having a wife (or both).^[2] An intervention gains 1 QAWY if it increases the expected amount of time you’ll spend happily married by 1 year (or the amount of time you’ll spend in a half-as-happy marriage by 2 years, etc). We do need some benchmark for a “happy marriage”; I’ll arbitrarily pick the 90th percentile of marriages across the population. Some factors which affect QAWY evaluation include spouse compatibility, age of marriage, diminishing marginal utility, having children^[3], and divorce probability. Conveniently, QAWYs don’t require the assumption of lifelong marriage - they can naturally account for the possibility of multiple consecutive (or even concurrent) marriages. With QAWY’s combination of theoretical elegance and pragmatic relevance, I look forward to their widespread adoption.

(To borrow a disclaimer from Chris' original post: seriously? Nope. I'm about 90% joking. I do think the general idea can sometimes be helpful, though.)

^{^}
Some version of micromarriages may still be useful - we just need to adjust them to measure an acute one-off event rather than a continuing chronic contributor to marriage. The most natural one is probably to think of a micromarriage as a one-in-a-million chance of first meeting your future spouse at a given event.
^{^}
Unfortunately, this is still not fully inclusive. In formal contexts please use Quality-Adjusted Wedded Years instead.
^{^}
The likelihood of which should of course be measured in units of microchildren (but not microkids, which I'm reserving for a very small chance of a very small joke, like this one).