Take family of 4, AGI 100k. Total tax rate 18%.

SS+MED 8k.
Standard deduction 13k + exemptionx4 14k =27k. 401k 10k 
Taxable income 63k, tax due about 6.5k/ 4.5k with child tax credit.
State tax: varies, say 5k.

Total: about 18k.

 AGI 200k will get total tax rate of about 30 %.