Ranking needs to be adjusted. I like the new Bronze, Silver, Gold, etc levels, but the way you get them needs some work. In FFA, I just got diamond 1, which beat January’s placement rank of Platinum 5, which i’m pretty excited about. But in slayer and team arean, I got Gold 4 and 5? What in the world? In almost all of those games, I was leading the team with a positive KD, and we still lost which is pretty sucky. I got placed into Platinum 1 last season, and now i’m in gold. These ranks should take BOTH individual performance into account, and if you team wins/loses. Your rank alone should not be determined by bad players on your team, causing you to lose.
It looks like the ranking games revolve around your individual performance and not so much the win/loss… there have been plenty of posts from people who pretty much lost all their games but still ranked well.
It doesn’t appear to be purely K/D… or at least not the raw value. I suspect it’s your place on the ladder of KDA (and the relative ranking of those who finished above or below you).
If it’s based around a chess like ELO system… then the first few games are the critical ones (where your ranking will make large swings).
And finally, your previous ranking is taken into account. At the very least it influences your opponents in the (critical) early ranking games. It is certainly used to stop you deliberately “deranking”.
The early seasons seemed to over rank people (pretty much anyone who got stuck at level one in their division is probably out of their depth)… and 343i seem to have adjusted their algorithm a bit so that you tend to be marked a bit harder (you can always work your way up… but you can’t drop back).
Anyway, in your case… Gold 5 and Platinum 1 are pretty much side by side… and it wouldn’t take a couple of days to work your way back up. There is always going to be a little margin of error in any statistic that only takes a small (ten game) sample. You were probably just a bit unlucky not to get good enough opponents in the early games to show the algorithm your platinum chops.
placement takes everything into effect so KDA, win/loss etx. moving in rank is purely dependent on win/loss