Since some people are downvoting for bad reasons, I'll just toss in this anecdote: My parents were audited by the IRS for 5 years straight. They were convinced

Since some people are downvoting for bad reasons, I'll just toss in this anecdote: My parents were audited by the IRS for 5 years straight. They were convinced that my father "was hiding income through losses in your wife's business." My father was a surgeon; my mom ran an antiques shop. The IRS auditors setup camp in our living room for a month going on five years. That quote was straight from the lead auditor's mouth. I remember it very starkly as a young teenager. (I said hi to them each morning on my way to and from school) It really peeved me that they viewed my mom (the woman) as a failure and only a place for my father (the man) to "hide income." Every year they came to the same results. My mom's bookkeeping was a mess, but she always overpaid her taxes and we got a refund at the end of the audit. The best kicker? My mom made more than my dad. The IRS thinks women should make less than men (by word and by audit). As for the historic reasons of this thinking, see my reply below. If married filing jointly isn't sexist, why are the income brackets different? Even for married filing separately, why are they different than for single people? Sit and think about it for a minute.