KIRKLAND, Wash. (AP) — Bill and Melinda Gates are pushing back against a new wave of criticism about whether billionaire philanthropy is a force for good.

The couple says they’re not fazed by recent blowback against wealthy giving. It’s come in high-profile moments at the World Economic Forum and the shifting political conversation about taxes and socialism.

Melinda Gates told The Associated Press that the attacks are about wealth, not philanthropy.

The latest criticisms challenge whether their level of wealth is good for society and whether it’s functional to rely on the generosity of the very rich to fix its problems. The couple’s nonprofit work relies on the tax-exempt fortune they hand to the Bill and Melinda Gates Foundation.

The Gateses have released their annual letter Tuesday reviewing their work and vision.