Thanks all for your input, and thanks Felix for writing such a detailed reply. I am leaning towards 100, but I have to say, the question isn't very well written. As jason says, to which are you comparing? The median or average? The worst? This obviously massively changes the answer. 

Hi all, this is probably very cheeky but here goes anyway. I've been trying to career switch into something EA and so am currently applying for the Charity Entrepreneurship programme. One of the application questions puzzled me. Having read Doing Good Better I was pretty sure of the answer but then questioned it again. The question is "When comparing charities in the world I'd estimate the most effective ones are a) Closest to 100x better b) closest to 10,000 x better." The other options are clearly wrong so won't list them here. 

My initial reaction was to pick a) because thinking back on the book I remember William saying that 1 QALY for DMI is about $10, bednets about $100 and the US is willing to spend $50,000 per QALY. But the US isn't a charity. And I know that some animal charities can be very effective but you can' t measure their effectiveness in QALYs. So I was just wondering what other people would pick, a) or b)?