Someone should sticky an explanation.
Rank is based on your qi (number of games played) level within JUST YOUR BELT. The more qi you have, the higher your rank.
Example:
If you have 19 qi, (one game from yellow belt), then you will have a higher rank, because most of the other white belts do not have as much. Once you get the 20th qi and you upgrade to yellow belt, your rank will go back down because almost everybody who is a yellow belt has more qi than you.
If you have the same amount of qi as somebody else, then whoever has the higher win/games played percentage will get the better rank.