The good news is that this figure has been rising steadily in recent years. Americans like to think that when it comes to foreign aid, we are a generous nation. But in fact, even when both government aid and private charity are added together, we give, in proportion to gross national income, less than half as much as nations like Denmark, the Netherlands, Norway and Sweden.

As for all that junk mail you are getting from charities: Ignore it. Would you buy a used car with no warranty because the owner tells you it runs well? Not likely. At a minimum, you’d do a test drive, and if you don’t know much about cars yourself, you’d be wise to get an independent agency to check it over.

It’s the same with charities. Not every charity will use your money well. Finding out which ones are effective isn’t easy. Don’t look just at the percentage of income that a charity spends on administration. It might spend very little on administration, but because it doesn’t employ enough staff to assess the programs it supports, its programs may do no good at all. GiveWell has pioneered rigorous assessment techniques for charities. Take a look at its top recommendations (www.GiveWell.org). Some other charities may be highly effective, even though their methods don’t lend themselves to GiveWell’s quantitative methods of assessment, so on www.thelifeyoucansave.com, I’ve listed some others that are worth considering.

There are other causes that I haven’t mentioned that are worthy of support: reducing the vast universe of pain and suffering we inflict on animals, for instance, or combating climate change. The guiding principle is to give where you will have the most impact.

Peter Singer is a professor of bioethics at Princeton University and laureate professor at the University of Melbourne.