Ezra C: You are saying that you would increase your giving by $1 for every $1 of tax benefit that the government offers you. That would be an elasticity of 1.0. It is great that you are that generous, but studies of the real world effect of tax incentives, like the ones examined in the survey by Hungerman and Otoni-Wilhelm cited in my post, find that on average, people are not that generous. They only increase their giving by a fraction of a dollar for each dollar of tax benefit that is offered. Different studies based on different kinds of giving, different time periods, different states or countries studied, different estimates etc. come up with different estimates of the fraction, but the estimates generally fall in the range of 20 to 50 cents extra giving for each dollar of tax benefit offered, with more studies clustered toward the lower end of that range of estimates. Partly that is because some people are less generous than others, partly because some people don’t itemize, and so on.