Are the Rich undertaxed?

There’s been a lot of Robin Hood politics of late, with talk of punishing “the rich” and giving more to low income earners. I’m certainly no fan of middle-class welfare, but should higher income earners be paying a higher percentage? The following stats come from this ATO document (excel file) which show the percentage of income tax paid by percentile:

Percentile % Income earned % tax paid
Top 1 9.4 16.5
Top 5 20.8 32.3
Top 10 30.3 43.6
Top 25 51 65.1
Top 50 75.1 86.3

Thoughts?