WASHINGTON -- With one in three of the nation's babies born to unwed parents, Congress is giving states a challenge: Reduce the out-of-wedlock birth rate the most and share in $100 million.

Now, four states and the District of Columbia have been notified by the Department of Health and Human Services that they are the first year's winners, provided they can prove that abortions also declined.The winners were diverse -- California, Michigan, Alabama, Massachusetts and the district -- and officials were puzzled to explain their success. Massachusetts began with one of the lowest unwed birth rates; D.C. had the highest.

"Why these five states? I don't think there's much we have to say on that," Michael Kharfen, a spokesman for the Department of Health and Human Services, said Thursday.

The winners had their own guesses.

"There's been a message about welfare changing and changing fairly radically," said Joel Sanders, who directs Alabama's welfare reform program. He also credited the strong economy.

But he acknowledged that virtually every state has tough welfare rules and a strong economy. "That's where the luck comes into it," he said.

In Massachusetts and California, officials credited programs that give communities money to create pregnancy prevention programs, generally focused on teenagers.

California also credits increased access to birth control and evolving attitudes.

"It's a combination of programs and changing social mores among families in California, where out-of-wedlock pregnancy is no longer as easily accepted," said Anna Ramierz, who runs California's Office of Family Planning.

Nationally, about one in three babies is born to a single mother. The figures range from 16 percent in Utah to 65 percent in the District of Columbia.

The winners have until Sept. 1 to prove that abortions did not increase between 1995 and 1997. Those that do will share the $100 million. An additional $100 million will be awarded in each of the next several years, based on subsequent data.

Congress included the bonus money in the 1996 welfare bill, though it was hardly noticed at the time. It was included to appease lawmakers who wanted to limit welfare payments when a mother has additional children while on welfare.

Instead, states got a lucrative incentive to reduce their out-of-wedlock birth rates.

The contest includes all births outside marriage to teens and adults, to families on and off welfare.

While many states have targeted teenagers, teenage moms account for only one in three unwed births.

And though states credit the welfare overhaul, the first bonuses were based on statistics from 1996 and 1997, when the changes were just beginning. The welfare law creating the bonuses wasn't signed until August 1996.