One of the considerable challenges to compiling the Slate 60 is figuring out how and what to count. Throughout our history, our methodology has evolved. As we have for the past few years, we count pledges and donations made to foundations or charitable organizations. To avoid double-counting, we do not count gifts made by foundations, and we do not count payments made on previous pledges. So, if you wonder why well-known philanthropists such as Bill and Melinda Gates and others do not appear on the list this year or in the recent past, it may well be because they are focused on making payments on previous generous pledges.