The more equal the income of your spouse, the more taxes you pay. If both your incomes are equal marriage will might cause you to pay tax.

http://en.m.wikipedia.org/wiki/Marriage_penalty

Contrast this to Singapore. Equality is rewarded. If both partners earn a higher income that means you can afford a maid. But you are eligible for a tax rebate on the maid if you are married. Of your parents are old and living in your house, another tax break.

http://www.iras.gov.sg/irashome/page.aspx?id=9902