At CNNMoney's request, the Tax Institute of H&R Block calculated the 2013 federal income tax bill of a dual-earner married couple with two young kids -- and compared it to the tax bill of a single person without kids.
We assumed that both the couple and the single person made $100,000 in wage income. (See below for the other assumptions we made.)
And we looked at what their federal income tax burden would be across three cities: Seattle, Topeka and Queens, N.Y.
What we found: The single person paid much higher taxes in all three places -- between three and four times more.
In Queens, the single person's bill came to $11,660 versus $3,076 for the married couple.
In Topeka, the single person paid $13,410, and the married couple paid $4,066.
And in Seattle, the tax bills came to $12,360 versus $3,286.
The yawning gap held up even though each city has different state and local taxes, which influence how much federal tax people pay.
Why the huge disparity: The reason for the big differences is mostly a host of child-related tax breaks the couple can take on their federal return -- such as the child tax credit and other breaks for child care and dependents.
Image: Tax form, via Shutterstock