Arrests of men who drive under the influence still greatly outpace those of women. But while the number of arrests of men is declining, the number of arrests of women is gradually rising.

"We've come a long way, baby, and this is not a good way," said Gail D'Onofrio, chairwoman of the emergency medicine department at Yale School of Medicine.

As the state police continue this week with their annual holiday crackdown on drunken driving, a gender breakdown for arrests in recent days is not available, said spokesman Lt. J. Paul Vance.

But over a period of years, state statistics show that women are becoming a larger percentage of all drunken drivers in Connecticut - rising from 17.4 percent of all arrests for driving under the influence in 1997 to 21.7 percent in 2006, the latest figures available, according to the state Department of Public Safety.

That might not seem like a dramatic shift, but the trend is clear: Arrests of men fell by 17 percent during those years, while arrests of women have been flat or slightly up over the decade.

Nationally, the trend is slightly different, but with the same end result: The number of women arrested for DUI increased by 28.8 percent between 1998 and 2007, while the number of men arrested for DUI dropped by 7.5 percent, according to U.S. Department of Justice crime statistics.

The reasons for this shift are diverse, according to academics, insurance experts and law enforcement officials.

More binge drinking among younger women and strict enforcement applied more often to women drivers might be contributing to the trend - along with a cultural change that has put more women on the road and brought them into roles of responsibility, experts said.

Young women are binge drinking more than in the past to keep up with their male counterparts, nationally and in Europe, said D'Onofrio, who is widely recognized for her work studying patients for alcohol and drug use. This is especially dangerous because women become more impaired from alcohol than men, partly because women have proportionately less water in their bodies than men, she said.

But binge drinking among young women might not explain the whole shift.

The answer might lie in the way that laws are enforced. Police are less lenient on women than they had been in the past, said Henry Kranzler, associate scientific director of the Alcohol Research Center at the University of Connecticut.

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Men account for the bulk of arrests for drunken driving - 78.3 percent of arrests statewide in 2006 compared with 82.7 percent a decade before. But some men might be changing their behavior in response to increased punishments and a greater societal disapproval in the past 10 years, Kranzler said.

The National Highway Traffic Safety Administration released a report this month that said the overall fatality rate from car crashes declined from 2007 to 2008. The same is true for crashes involving drunken men and women: There was a decline for both from 2007 to 2008.

"If women are drinking more, there should be a greater increase in the fatalities related to drinking, and because there isn't . . . it really does suggest that there's differential enforcement," Kranzler said.

Connecticut State Police spokesman Lt. J. Paul Vance disagrees with Kranzler's suggestion.

"I don't think we treat males or females differently today as compared to yesterday," he said.

One thing is certain: The insurance industry has taken note as the number of women drivers has increased in the past several decades. In 1963, 40 million motorists were women, accounting for 43 percent of drivers, said Loretta Worters, a spokeswoman for the Insurance Information Institute.

"Today, more than 88 million women are licensed drivers, almost half of all motorists in the U.S.," she said.

Premiums for young women, in particular, have risen significantly, closing a gender disparity. Thirty years ago, young women drivers paid 46 percent above the base rate for adult drivers while young men paid 187 percent above the base rate. Today, young women pay 120 percent above the base rate and men pay 185 percent, almost exactly where they were.

"Over many years, across the nation, we have seen an overall merging of the rates charged between men and women," said Ted Mitchell, a spokesman for MetLife Auto & Home. "This is likely the result of a number of factors - such as the fact that women are more equally participating in this country's economic life and, therefore, are on the road more and driving many more miles."

"As the driving habits of women more closely resemble those of their male counterparts," Mitchell said, "instances of aggressive driving and drunk driving have increased, and a woman's auto rates are likely to be similar to those of a similarly situated male counterpart."