Thanks!

My main reason for trying to be mostly risk-neutral in my donations is that my donations are very small relative to the total size of the problem, while this is not the case for my personal investments. I would donate differently (more risk-averse) if I had control over a significant part of all charitable donations in a given area. In particular, I do not endorse double-or-nothing gambling on the fate of the universe.

You make a good point that OP is more likely to make judgements regarding small donation opportunities, so I'll have to revise my position that small donors should specifically seek out smaller organizations to donate to. But the same argument for "topping up" OP donations could equally be made to support simply donating to an EA fund (which I expect will also take into account how their donations funge with OP).

I agree with the overall conclusion of this post but not completely with the reasoning. In particular, there is an important difference between allocating investments and allocating charitable donations in that for investments it makes sense to be (at least somewhat) risk averse, while for donations a simple strategy maximizing expected benefits makes perfect sense.

Even a risk-neutral approach to charitable donations will have to spread its investments however, because there is only so much money that the most effective charity can absorb before reaching its funding gap, which makes the next best charity the new most effective one.

For a big organization such as OP, this can become a real problem for a cause area where there are many charities with high effectiveness but (relatively) low funding gaps. This might be part of the explanation why OP pays more to global health, where there are very large organizations that can effectively absorb a lot of funding, over animal welfare.

For small individual donors, this means that there are likely opportunities to make very effective donations to organizations that might be too new or too small to be picked up by the big donors. You might even help them grow to the size where they can effectively absorb much larger donations.

So to reiterate, I think it makes sense to prefer donating to smaller charities and cause areas as an individual donor, but the reason is that they might be overlooked by the big donors, not to "balance out" some imaginary overall EA portfolio.

Thank you for this detailed reply! This agrees with my intuition that the numbers the volunteer told me were not at all realistic. My main goal with writing this post was not to question the effectiveness, but to bring it to the attention of the community that there is value in making this kind of information (such as what you write in this comment) available publicly, instead of the current silence on mega-charities.

Where can I find more information about the tax deductability in the Netherlands? I can't find any information on the main  donor lottery page.