This circle represents the total 32-bit address space with the black region being those addresses that cannot be used (224/4, 10/8, &c); the gray circle represents the 3.7B addresses remaining.  The allocated space, currently 52.3% of the gray, is what the RIRs work with and, in turn, delegate down to IIRs.  The orange region represents the portion of the address space which is assigned to the ISPs and individual networks.  We haven’t measured the size or growth of this or the ‘delegated’ address (not illustrated) regions yet; these will be analyzed in the near future.