I don't think GiveWell would rule out a charity because it considers the human element in a way that makes it less economically efficient.
The question is just, is it overall more efficient at broadly "bettering people's lives" in a way they can measure? That's it. If you can show that letter writing is a worthy trade-off by e.g. looking at long-term impacts, I'm sure they'd be for it.
Perhaps you object to the fact that they require measurement. Fair enough, the best things in life are free. But the "bags of grain" (really, "bags of malaria pills") approach is already at a disadvantage to the "give someone a flock of chickens" approach, because the latter tells a story and tugs at our hearts. That doesn't mean it's worse, but I think GiveWell's thesis is, that also doesn't mean it's better.
The question is just, is it overall more efficient at broadly "bettering people's lives" in a way they can measure? That's it. If you can show that letter writing is a worthy trade-off by e.g. looking at long-term impacts, I'm sure they'd be for it.
Perhaps you object to the fact that they require measurement. Fair enough, the best things in life are free. But the "bags of grain" (really, "bags of malaria pills") approach is already at a disadvantage to the "give someone a flock of chickens" approach, because the latter tells a story and tugs at our hearts. That doesn't mean it's worse, but I think GiveWell's thesis is, that also doesn't mean it's better.