$i'=i^{-1} \bmod p$, prove or disprove that $\lim_{p\to \infty}\frac{1}{p^3}\sum_{i=1}^{p-1}ii'=\frac{1}4$

Solution 1:

For some numerical support, here's a plot of $S(p)/p^3$ for the first $4000$ primes.

enter image description here