[George Ford]

What blood banks want is for the 0-negs to return as frequently as possible, and everyone else to stay home (a slight exaggeration, but not by far). My blood costs more to collect than it has value, but they take it anyway so I don't tell my O-neg friends they told me to leave.

[Richard Williams]

What blood banks want is for the 0-negs to return as frequently as possible, and everyone else to stay home (a slight exaggeration, but not by far). My blood costs more to collect than it has value, but they take it anyway so I don't tell my O-neg friends they told me to leave.

i don’t know if that is true, but I am O-neg so that might explain why I get so many desperate sounding emails if I haven’t donated lately. Blood type might be an interesting variable to toss into any model. It might be a proxy for amount of effort spent on getting you to donate.