I really don't have anything on the Army side, but, I do have something that could be worth taking into account on teh navy side.
I don't believe it completely accounts for everything, as I do think there has been some "rank inflation" to have more officers than really neaded, however, i don't think it's fair to ignore all the facts either.
For the navy, you can't just take into account # of ships ... Need to also take into account the sizes of the ships, and their capabillities...
Ships today are bigger than they were in the past.
Ships today are faster than they were in the past.
So, a ship today is a bigger asset than a ship may have been in the past.
In 1945, your average destroyer was a fletcher class with total displacement about 2500 tons.
During the 50s, destroyers grew, total displacement around 5000 tons.
In the 70s, new destroyers were being built even larger, total displacement of over 8000 tons.
Current Destroyers of the Alreigh Burke class range from 8300 to over 10000 tons of total displacement.
Now, during WW2, battleships which were HUGE pretty much became obsolete .... and cruisers have since proven to be of margainal use due to their vulnerabillity to air attacks .... so they are being phased out.... So some of the "biggest" ships are gone ...
But then look at aircraft carriers ...
In the 1930s, the Yorktown carriers were about 30,000 tons with around 2200 people onboard...
In the 40s, the Independance class light carriers were built, they were smaller, only about 11000 tons (converted from cruisers)
In the 40s, the Essex class carriers were built ... (and in service until 1991!), they displaced about 40,000 tons when full...
Current carriers are the Nimitz class over 100,000 tons. Over 5000 people onboard the boat... that's ENOURMOS
Prior to the Nimitz class
So, when it comes to the destroyer and the carrier, the ships have grown quite a bit in size. They take a lot more crew to run, and are much more capable vs a destroyer or carrier of the WW2 days.
Modern carriers have much better range and speed vs the pre-nuclear days, and are essentially worth many of the older ships...
So, while the number of ships may not have grown, the overall capabillities of the navy have grown, so it would seem like the command requirements to handle such capabillities would also grow ... thus, changing the ratio of Admirals to Ships.