Hmm, I don't quite understand this methodology. This site lists my state, Massachusetts, as having a 3.29% individual income tax burden, but our income tax rate is a flat 5% (no brackets). I'm looking at the exemption list (https://www.mass.gov/service-details/view-massachusetts-pers...) and I can't see how it could possibly make that big of a difference.
The dependent exemption and old age exemptions definitely look like they could knock out 1.5% of income. If you have an income of 70k and two dependents, you would have an effective tax rate of 2.14%.