Suppose I am trying to optimize purely for altruistic impact , should I stay single or pursue a romantic relationship? Is there any relevant social science on the casual effects of each on productivity?
Intuitively, it seems like being single would be more useful since you would then have more time to dedicate to work. On the flip side, being in a relationship might help cut costs enabling more donating and could increase happiness to have an indirect effect on productivity?
If you want to try a work strategy that involves long hours then a positive successful relationship may be harder to achieve.
Otherwise I’d advocate you don’t instrumentalise your non-work time for impact. I know it’s a cliche but do what you enjoy. Instrumentalising your free time seems to make people less relatable (probably an understatement), less trustworthy, more prone to depression, less robust to sudden changes etc
Having a strong base, whatever it is for you, is pretty important I think. When impact stuff is going badly you don’t want to feel like everything is going badly. That kind of instability is going to have more Long term effect for your impact than a few thousand pounds a year in one direction or another.
Alex Foster's answer covers most of what I wanted to say, but I'll also note that thinking in this way...
On the flip side, being in a relationship might help cut costs enabling more donating and could increase happiness to have an indirect effect on productivity?
...is unlikely to be conducive to a successful romantic relationship, unless this thinking is secondary to thoughts like "I really like this person, they make me happy, and I also want them to be happy".
(There's a word for a relationship you form to cut costs, and the word is "roommate". There's a word for a relationship you form to increase happiness, and the word is "friend". As a bonus, it's easier to have multiple roommates or friends than it is to have multiple romantic partners.)
While I don't have an actual answer of any kind, I'd argue that a relationship can have "positive externalities" on altruistic endeavours, e.g. by discussing EA ideas much more frequently than you otherwise would (depending on your circumstances), and, in case the other person is into EA as well, keeping each other motivated. I personally would assume that my long term engagement in EA would drop quite a bit were it not for my relationship. That's certainly different for other people however, so this isn't anything more than one random data point.
As a side-note, relationship status is something that tends to be very personally important to people and it is not an area where I would generally ask people to sacrifice for EA impact. However, I am personally indifferent between relationship statuses, so knowing the effect on EA impact would be helpful.
Hm, my intuition goes the other way. I would assume being in a relationship increases your chances of convincing your gf/wife to donate at least a little, perhaps 10%, to your choice charity. I've never been in a relationship though so who knows.