The US Navy also attains its number of fleet assets by building up from zero. When you cut a carrier battle group, several escorting ships are cut, along with a carrier air group. Logically the number of carriers reflect one carrier forwardly deployed for every three carriers to sustain the fleet composition. When you wish to have a carrier deployed to the WestPac, three are required. When you wish to have a carrier deployed to Europe, three are required. We are up to six already. If you desire two carriers deployed to WestPac and Europe, twelve are required.
Simply put, the US cannot afford to do so much longer. After the Cold War many have suggested the US could easily have the same influence with just one carrier forwardly deployed to WestPac and Europe. Unfortunately, with the war on terrorism, in the eyes of Congress and the new administration the US requires one carrier in the IO as well. Nine is the magic number. But the IO is such a long distance, four carriers are required instead of three to sustain one. Thus ten is the magic number.
With one of the ten in a long term nuclear refueling process for the for-see-able future the US Navy should have eleven. Obviously, reducing to ten means the US Navy will have to sustain a carrier deployed to the IO with three instead of four. While this can be done, carriers in the IO will have to deploy for more than six months on a regular basis.
As it is with WestPac, the US Navy have been home basing one carrier in Japan. I suspect we could do the same with the IO with a home based carrier in either Singapore or Australia. But that requires considerable diplomacy. While Australia may welcome such a decision, I doubt New Zealand would.