How does a Pareto efficient equilibrium scale for n individuals?
If you are doing pairwise comparisons, then with $n$ individuals there will be $$\dfrac{n(n-1)}{2} $$ such comparisons.  You can write this as $\binom{n}{2}$ or as $\frac12n^2-\frac12n$ if you prefer.  

$1$ for two people, $3$ for three, $6$ for four and so on, known as triangular numbers