(CNN)"Is it fair that you have so much influence?" We've been asked that question more than a few times in the 18 years since we started our foundation. Our answer? No. It's not fair that we have so much wealth when billions of others have so little. And it's not fair that our wealth opens doors that are closed to most people. However, we do this work, and use whatever influence we have, to help as many people as possible and to advance equity around the world.