That report is very enlightening, and makes clear that the IRS is not doing their job WRT high-income non-filers. However, I don't see from its numbers how you

That report is very enlightening, and makes clear that the IRS is not doing their job WRT high-income non-filers. However, I don't see from its numbers how you arrived at > The top 1% of earners account for 70% of underreporting of income. since it only ever addresses non-filers and doesn't mention, from what I could see, percentile brackets for the filers it does discuss.