Where the golden rule in military causality ratio comes from?

WWII losses of various countries (lazily from https://en.wikipedia.org/wiki/World_War_II_casualties):
France: 210,000 Killed : 390,000 Wounded
Germany: 5 million Killed : 7.3 million Wounded
Hungary: 200K K : 90K W
Italy: 320K K : 275K W
Japan: 2.2M K : 326K W
Polan: 240K K : 766K W
Romania: 300K K : 330K W
SU: 10M K : 14.5M W
UK: 383K K : 376K W
US. 407K K : 671K W

Korean War (Wikipee, not including missing and deadly wounds and such):
RoK: 137K K : 450K W
US: 33K K : 103K W
Chiner: 114K K : 340K W
DPRK: 294K K : 230K W

Vitenam (Wikipee, also not including stuff):
RoV: 313K K : 1,2M W
US: 58K K : 303K W (about half not requiring hospital care)
Australia: 521 K : 3K W
NV and such: 800K K : 600K W

Muh Malvinas:
Arhentina: 649 K : 1600 W (11K captured)
UK: 255 K : 775 W

Grenade:
US: 19 K : 116 W
Granny: 45 K : 358 W

Yom Kippur:
Israel: 2700 K : 8K W
Arabs: 15K K : 30K W

Operation Iraq Occupation (2003)
US: 200 K : 550 W
In Iraqi case wounded is not known so.

All right I'm done with this.