Love your stats John!
I think it’s hard to understand how broken (and difficult) on-boarding really is until you face it yourself or you see concrete numbers (like those you cited above) from your own growing organization.
It’s hard especially for non-HR business leaders because they are the ones with resources (including their time) and knowledge to make on-boarding happen well but they usually don’t even remember how it worked when they were on-boarded.
We’ve on-boarded over 500 people within past 24 months and I can attest that the whole process was not easy and it would not be as efficient and valued by new joiners as it is without substantial initial efforts and continuous support — including of the fact that my boss personally does a part of on-boarding session every month and each of my fellow directors too.
Good luck with effort to fix on-boarding, it’s certainly needed!