"things are bit more nuanced that just one in three being active." - but that's the well worn rule of thumb used by people like the USN and the RN SSBN fleet WEBF
I just cannot believe that they are thinking of cutting the number of escorts NOW with the usual fairy-tale "we'll order a load more later" excuse. I think the RN needs at least 30 to cover the various roles the politicians keep loading on to them - remember what Nelson kept asking for................... frigates, not ships of the line