For every HOH competition you will ALL be ranked on best to worst. First place gets 16 pts, second place gets 15 pts, etc. For week two, first place gets 15 pts, second place gets 14 pts, etc.
If you have a tie with someone, you will all get the average points of the placings you take up. (Ex. Say you tie for 3rd with two other people during round 1. Usually 3rd, 4th, and 5th would receive 14, 13, and 12 points. That averages to 13 points and all three would get that score.
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There is a line of vulnerability. If you are above it (in green) you are safe from being nominated for the week. If you are below it (in yellow) you are in danger of being nominated and possibility evicted for the week. No matter where you are in the Power Ranking, if you come in first place in a HOH or POV you will win and be granted that power for the week. This means you can have the fewest points in the Power Ranking, but can be the Head of Household for the week. The Power Ranking only dictates who can be nominated or not.