INCOME tax rates have recently been raised slightly for some affluent people, and there is pressure for additional increases. But some economists say raising marginal income tax rates on high earners may miss the mark.

One reason is that the truly wealthy employ all kinds of legal means to minimize their tax liability, including shifting income around the world, deferring gains on their assets and many other sophisticated strategies. Another, though, is that taxes on ordinary income simply don’t apply to inheritance or investment, principal sources of wealth.

Under legislation that Congress approved on New Year’s Day the top marginal income tax rate for 2013 has risen to 39.6 percent from 35 percent for individuals on ordinary income over $400,000 and for couples on income over $450,000, while tax deductions and credits start phasing out on income as low as $250,000. But what is being taxed is often just a small portion of the income and wealth of the very richest Americans; unearned income, including unrealized gains and gains on investments, is either not taxed or taxed at a fraction of the top rate on wages.

Taxing wealth in addition to income is one way to make sure that the rich contribute more to government coffers. That would essentially be a tax on household assets like property, stocks, bonds, unincorporated businesses, trusts, art and yachts.