If a donor invites someone to join Charitocracy, or gifts someone with their first year's membership, Charitocracy keeps track of that relationship. In addition to showing you how much you've directly donated to Charitocracy, we also show you all the donations for which you're indirectly responsible.
Think of it as a tree where you're the trunk, perhaps a donor who invited you is the roots, and everyone you've invited or gifted into Charitocracy are the tree limbs. Everyone they've brought into Charitocracy are the smaller branches above that, etc. The impact you make on Charitocracy's winning causes from your direct contributions are hugely appreciated, but just imagine how your impact will multiply if you cultivate a healthy Giving Tree!
You won't know exactly how much other donors in your Giving Tree have donated, since you won't know how broad and high their part of the tree grows. Likewise, others won't know how much you've given, because your "roots" can't distinguish between your donations and the rest of the tree above you. Thus your level of generosity remains private (unless you explicitly choose to reveal it) and your place in the Giving Tree is only visible to donors whom you've invited and vice-versa.
If you signed up for Charitocracy without an invitation, please let us know if someone told you about Charitocracy so we can give your Giving Tree some roots!