[rdl]

There's risk and there's also inflation embodied in the capital gains. If you invest for 20 years, inflation can be a big percentage of a gain. It gets taxed as capital gains, which is one of the stronger arguments for a lower rate for capital gains than annual income.

(of course, sometimes annual income is ALSO the result of deferred compensation. Say a doctor spends 8 years making $30k/yr when she could have been making $120k, and then starting in year 9 makes $300k/yr for 8 years, then has children and leaves the workforce for 20 years (fairly common for female doctors in pediatrics, which is why there is an undersupply...). That doctor is paying way more total tax than someone with a more stable income.)