Last week, House Republican sophomores launched a new effort to abolish the so-called marriage penalty. This results when a husband and wife both work. Because of progressive tax rates, many pay more federal taxes as a couple than they would pay if taxed as individuals. Although the Contract With America promised to eliminate the marriage penalty, the recently enacted tax bill did absolutely nothing in this area. In fact, it actually made the problem worse.

The marriage penalty is exacerbated by provisions in the tax bill that phase-out as incomes rise.

• For example, the $400 child credit is eliminated for couples making more than $120,000 per year, but is available for singles with incomes up to $75,000.

• Thus a husband and wife each making between $60,000 and $75,000 would get no child credit if married, but would save $400 in taxes per child if single.

• Other provisions that aggravate the marriage penalty are the education credits and expanded IRAs.

Attacking the marriage penalty would have been a far better way for Republicans to appeal to conservative Christians and pro-family groups than the child credit. As economists James Alm and Leslie Whittington have shown, the marriage penalty reduces the probability that a couple will marry and increases the likelihood of divorce. Thus elimination of the marriage penalty should be very attractive to this constituency.

Although professional women are often at odds politically with Christian and family groups on issues like abortion, they are united on the marriage penalty. In fact, the "soccer moms" are probably the largest group affected by the marriage penalty. This is a key swing group that voted for Republicans in 1994, but turned against them in 1996. Doing something about the marriage penalty could bring them back in 1998.

Supply-siders like the idea of reducing the marriage penalty because it imposes higher tax rates on many Americans, which reduces their incentive to work, save and invest. These disincentive effects are so large that economists Martin Feldstein and Daniel Feenberg estimate that increased labor supply by married women would offset much of the revenue loss from elimination of the marriage penalty.

Finally, liberals would also support abolition of the marriage penalty because the largest penalties fall on the working poor (see figure). Because of the way the Earned Income Tax Credit works, a couple with two children where each spouse earns the minimum wage pay a marriage penalty of as much as 17 percent.

In short, both economics and politics strongly support elimination of the marriage penalty. The House Republican sophomores are right to make this their key tax issue.