As an individual, no donation I make makes a noticeable difference, ie. it’s all rounding errors.
But, if everyone though so, no one would donate and the small donor part of charities funding would evaporate and that would make a difference.
Economies of scale and transaction costs favor giving one big chunk of money to one charity, this minimizes the amount of money wasted on administration and marketing.
If charity == uncoordinated wealth redistribution, then it doesn’t matter who gets the money (but by this reasoning, it doesn’t matter how many recipients either)
“Selfish” charities (giving only to your own community, alma matter, family, kids, or donating to the public library or museum that you use) favors giving to fewer charities, the more organizations you give to, the less and less likely that those donations will positively impact you.
Membership == political clout. If I care about chimp rights and voting rights, if I only contribute to chimp rights, congress thinks I don’t care about farm animal rights. I should split up my contributions to give each group head count.
I don’t know which charities are effective, give money to many charities to maximize the odds that one of them is effective.
Some charities are funded mostly by small donors and care what the small donors think, others are funded mostly by large donors and presumably care less about what small donors think.
Obviously some charities should be eliminated from consideration because they are too small to make a difference with that money or put it to significant use (the 6 member animal right group at a community college), or because they squander it on administrative and marketing costs.
A point that doesn’t fit in– charities with low “leverage” shouldn’t get as much money. If you give money to feed children, it creates positive effects for their family, siblings, etc. College scholarships for the middle class, generate benefits for one person– the effects don’t spread far.
Tipping points. Smoking is mostly a won battle. Sort of. Gay rights are at a tipping point. In the US, veganism is far from a tipping point, but in England and German, it might be close to a tipping point. Small donations make the best impact on issues near a tipping point, where the whole of society is about to change their mind, and just needs a $20 shove. Or 100,000 $20 shoves.