[DSpinellis]

Nice benchmark! This is a (not at all efficient) awk one-liner.

awk -F\; ' $2 > max[$1] { max[$1] = $2 } !($1 in min) || $2 < min[$1] { min[$1] = $2 } { sum[$1] += $2; count[$1]++} END { for (n in sum) printf("%s=%.1f/%.1f/%.1f, ", n, min[n], sum[n] / count[n], max[n])}'

Can't see how dgsh could be applied to it.