I read this in the UK but it was forty plus years ago so the details are hazy. It could have been a novelette.
There are two Earthmen on some alien planet, I can't remember what their mission was. The inhabitants are very similar to humanity but possibly longer legs and very slender.
The females give some kind of medallions out to males if a satisfactory sexual coupling takes place, the more a male has, the higher his social status. Because the Earthmen have a sturdier build than the native males they score much higher and are very successful.
One Earthmen develops his own score system, so instead (for example) of having several dozen silver medals pinned to his chest he has a gold that's worth ten of the silvers - please note that I'm not cognisant on these specific colours, I'm just trying to recall the actuality.