It gets more complicated if one tries to work out numbers on the basis of supposed unit strengths in some armies.
IIRC:
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German units with the same designation e.g. battalion or division, in WWII could have wildly different numbers depending upon their function and posting, such as a garrison unit having a fraction of the number of troops in a combat unit with the same designation.
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Japanese divisions numbered above 100 had about half the number of troops in those established earlier and numbered below 100.
Then there are differences between armies which make comparisons difficult. For example, the Japanese used about 60,000 Allied POWs on the Burma Railway plus about 250,000 to 300,000 Asian civilians as conscripted labour, where the British or US armies would usually have used military engineers etc on the same sort of task. The Australians made heavy use of native porters in Papua New Guinea on foot transport in rugged country where in Europe the equivalent Allied task would have been carried out by military transport corps.
Then there is the question of: Supporting whom? Significant efforts were made by American and British forces to supply the Chinese forces over The Hump for several years in WWII. They weren’t combat troops. They weren’t supporting their own armies. But they would on a simplistic calculation of troops in support roles throw out the ratio of, say, American service people supporting American combat troops in that theatre. The same applies to various other odds and sods dotted around the globe during WWII, such as the non-Soviet Allied effort to supply the Soviets through Iran.
If one had access to all relevant information and nothing else to do for about twenty to fifty years, I think it might be possible to work out a ratio of support to combat troops with some accuracy in a given campaign in WWII, but I doubt it could be done even for a given theatre, let alone the whole of WWII or any other war.
As for current armies, in the West the first thing we’d have to do is work out whether policy wonks and media officers etc are support troops, or just a waste of space (or food bandits as they were sometimes called in the Australian Army in the past) which should be excluded from all calculations related to military activities.