My marital status is single and according to the Arizona state income tax brackets my taxes should be 4.24%. But I was only required to pay ~2.0%, I cant understand why.

I calculated my state income taxes for 2016, and Ive looked at what my employer deducts for each paycheck, and the percentages Im seeing are coming out much lower than I would expect for the Arizona state income taxes at my salary. I cant understand why there is discrepancy.