How British and American admiral numbers compared

How did the Royal Navy's number of rear admirals compare with the US Navy at the start of the Second World War?

They were broadly similar in number, although the Royal Navy had done relatively little housecleaning of its flag list.

The Royal Navy and US Navy began the Second World War with broadly similar numbers of rear admirals. The Royal Navy had done relatively little institutional housecleaning, so its flag list retained considerable depth. A British total can look unusually large when viewed without a similar-scale navy for comparison. This was a broad comparison rather than a precise establishment count.