[Note: This originally came out of a post on the Facebook group, which was then reversed in light of Gregory Lewis's expert comments. The substance of this article is his; any errors are mine.]
If no one donated blood, a lot of trauma/hemorrhage victims would die, and the world would be a lot worse off. The average unit of blood donated goes pretty far, in terms of the expected value of the good it does. However, when considering whether or not to donate, we need to evaluate the counterfactual difference our actions make. That is, rather than looking at the average donation, the relevant measurement is of the marginal donation. This brings up the following considerations:
1) As it stands, a substantial number of people already donate regularly, and will continue to do so whether or not the (comparatively tiny) EA community does too.
2) Truly life-or-death situations are a minority of transfusions, and these are pretty much already covered by the existing supply. In fact, hospitals almost always keep an emergency reserve of O- specifically for these cases, so it's very rare that someone directly dies for lack of compatible blood. Because a large number of transfusions/donations happen each day, and blood product can often be transported to different hospitals to meet local shortages, projected supplies are relatively easy to forecast within a given margin of error, so it is possible for hospitals to maintain this emergency supply to handle urgent cases.
Thus, the effect of an additional donation to the existing supply is to help cases where the patient wouldn't be directly saved from death, but a transfusion would improve the quality of their recovery. Nailing down exactly how many QALYs this typically adds is very difficult to track, and probably hasn't been done in a rigorous way. However, there is reason to believe this number is not that high.
In the UK, a unit of red blood cells (RBCs) costs about 120 pounds. While financial incentives don't translate seamlessly into extra donations, this is roughly this price at which more supply can be obtained, so it roughly reflects the medical field's impression of how valuable it would be to do more outreach per unit. Furthermore, the typical cutoff for whether to fund treatment is ~20,000 pounds/QALY, which is much less efficient than the ~130 pounds/QALY one can get by donating to the AMF. (For more detail on these numbers, see this guesstimate and this explanation of it.)
Thus, for blood donation to be anywhere near as effective as the AMF (in terms of paying 120 pounds/unit for more product), the medical field would have to be undervaluing the effectiveness of blood donations by 2 orders of magnitude. Despite the lack of rigorous calculations done in the literature, a collective miscalculation of this magnitude seems implausible given the feedback mechanisms which exist in medicine, not to mention the tacit knowledge hematologists have developed from making these tradeoffs.
The role of effective altruism is to look for, and seize upon, moral opportunities that have been unfairly passed over by society at large. GiveWell-recommended charities, for instance, may sometimes get positive comments from economists, but receive insufficient funding to fully exploit the ethical gold mine that is their cause area. In the case of blood donations, the medical field generally has ways of spotting and filling in the cheap and obvious ways to save more lives, so our time is better spent on causes that aren't being watched over as carefully.
That said, there are occasional cases where emergency supplies dwindle. When this happens, specific appeals are made, and in these cases it probably is effective to lend some helping hemoglobin. Less crucially, regular donors often drop out on holidays and during the winter (due to colds/flu), so if one is inclined to donate, those are the best times to do so.
This seems to confuse costs and benefits, I don't understand the analysis. (ETA: the guesstimate makes more sense.)
I'm going to assume that a unit of blood is the amount that a single donor gives in a single session. (ETA: apparently a donation is 0.5 units of red blood cells. The analysis below is correct only if red blood cells are 50% of the value of a donation. I have no idea what the real ratio is. If red blood cells are most of the value, adjust all the values downwards by a factor of 2.)
The cost of donating a unit is perhaps 30 minutes (YMMV), and has nothing to do with 120 pounds. (The cost from having less blood for a while might easily dwarf the time cost, I'm not sure. When I've donated the time cost was significantly below 30 minutes.)
Under the efficient-NHS hypothesis, the value of marginal blood to the healthcare system is 120 pounds. We can convert this to QALYs using the marginal rate of (20,000 pounds / QALY), to get 0.6% of a QALY.
If you value all QALYs equally and think that marginal AMF donations buy them at 130 pounds / QALY, then your value for QALYs should be at most 130 pounds / QALY (otherwise you should just donate more). It should be exactly 130 pounds / QALY if you are an AMF donor (otherwise you should just donate less).
So 0.6% of a QALY should be worth about 0.8 pounds. If it takes 30 minutes to produce a unit of blood which is worth 0.6% of a QALY, then it should be producing value at 1.6 pounds / hour.
If the healthcare system was undervaluing blood by one order of magnitude, this would be 16 pounds / hour. So I think "would have to be undervaluing the effectiveness of blood donations by 2 orders of magnitude" is off by about an order of magnitude.
The reason this seems so inefficient has little to do with EA's quantitative mindset, and everything to do with the utilitarian perspective that all QALYs are equal. The revealed preferences of most EA's imply that they value their QALYs much more highly than those of AMF beneficiaries. Conventional morality suggests that people extend some of their concern for themselves to their peers, which probably leads to much higher values for marginal UK QALYs than for AMF beneficiary QALYs.
I think that for most EAs donating blood is still not worthwhile even according to (suitably quantitatively refined) common-sense morality. But for those who value their time at less than 20 pounds / hour and take the numbers in the OP seriously, I think that "common-sense" morality does strongly endorse donating blood. (Obviously this cutoff is based on my other quantitative views, which I'm not going to get into here).
(Note: I would not be surprised if the numbers in the post are wrong in one way or another, so don't really endorse taking any quantitative conclusions literally rather than as a prompt to investigate the issue more closely. That said, if you are able to investigate this question usefully I suspect you should be earning more than 20 pounds / hour.)
I'm very hesitant about EA's giving up on common-sense morality based on naive utilitarian calculations. In the first place, I don't think that most EA's moral reasoning is sufficiently sophisticated to outweigh simple heuristics like "when there are really big gains from trade, take them" (if society is willing to pay 240 pounds / hour for your time, and you value it at 16 pounds per hour, those are pretty big gains from trade). In the second place, even a naive utilitarian should be concerned that the rest of the world will be uncooperative with and unhappy with utilitarians if we are less altruistic than normal people in the ways that matter to our communities.
Good comment / I agree.
Nitpick (not important to read):
"A unit of red blood cells (RBCs) costs about 120 pounds"
"a donation is 0.5 units of red blood cells"
So 0.5 unit / donation * 120 pounds / unit = 60 pounds / donation
A donation takes the time to go there and get the blood out, plus the lost productivity from feeling weaker (assuming you were going to do something productive counterfactually); I don't know what's that number, but I'd put it at about 1 hour. So ~60 pounds / hour.