I don’t think there’s any good way to know or collect that information.
From recent leech calculations via my site at wanikanitools-golang.curiousattemptbunny.com (admittedly a small sample size), I’m able to put together some basic categorizations:
Mild (leech for 10% to 20% of people)
Yellow (leech for 20% to 30% of people)
Red (leech for 30%+ of people)
Do these seem to fit the scale more or less?