If an allowance didn't limit her, Ryan Boucher would quickly expand her music collection beyond the Spice Girls, Sublime and Mariah Carey. At least the 13-year-old girl can go to the mall and dream about compact discs.

"I go in and I can stare at them for five hours - not buy, just stare at them," the Rye, N.Y., resident said. "It's so difficult to decide on just one."Ryan and her girlfriends are behind a big change in the music industry.

Females bought more music than males last year for the first time since the recording industry began keeping statistics. Teenage fans of the Spice Girls, Hanson and the Backstreet Boys are leading the way.

Female buyers outnumbered males by 51 to 49 percent, compared to a decade ago when men outnumbered women buying music by 57 to 43 percent, according to the Recording Industry Association of America.

"It does seem that there are a lot more women in the store than there used to be," said Michael Williams, general manager of Tower Records in Long Beach, Calif. "The music, more than in the last number of years, seems to be very female-oriented."

It's no stretch to declare women the tastemakers in today's music scene. Pop music and heart-tugging ballads - think Natalie Imbruglia and Celine Dion - are in style. Heavy, dour rock is out.

Although statistics from phone surveys showed only a slight increase in the number of teenagers buying music last year, their role in making hits of the "Titanic" soundtrack and Aqua's "Barbie Girl" have made the industry take notice.

Girl power - just as the Spice Girls preach.

Asia Werner's been buying a lot more music than usual lately, but her heart belongs to the Backstreet Boys. The 14-year-old girl gives a you-have-no-clue look to anyone who wonders why. Just look at their pictures.

Her friend, Rachel Colon, scanned a Manhattan store last week for Spanish music and rock CDs from Bush and Oasis. And for fellow customers.

"There are hardly any good-looking guys here," Rachel complained.

Girls screaming for Frank Sinatra, Elvis Presley, the Beatles and the Backstreet Boys are part of music's history. More than ever before, they have role models to scream for, too.

Jewel, Fiona Apple, Sarah McLachlan and the Spice Girls all established themselves in the past year. McLachlan's Lilith Fair, a concert tour featuring female artists, was the sensation of last summer.

"There have been some pretty potent female artists out over the last 18 months that young women have really gravitated toward," said Polly Anthony, president of Epic Records and 550 Music, both Sony labels.

Many of the videos on MTV these days feature female artists, said Judy McGrath, MTV's president. It wasn't so long ago where that was unusual, she said. Now there's less polarization between the sexes musically and female fans are more comfortable asserting themselves, she said.

"You don't just like your boyfriend's music," McGrath said. "The guys don't call the shots anymore."

VH1 two months ago began airing "Women First," a show devoted to videos by female artists. Only women perform at this month's "VH1 Honors" concert.

"If you want to call it a bandwagon, we've jumped upon it," said VH1 executive Jeff Gaspin.

It was mostly female buyers that made Elton John's eulogy to Princess Diana, "Candle in the Wind 1997," the best-selling single of all time.

Sales have been measured by gender only since 1985, but the people in the recording industry believe men outnumbered women as buyers before that, too, because fewer women were working.

New York's WHTZ radio sensed a mood change two years ago and switched from alternative rock to Top 40. Now, 70 percent of its telephone requests are from females, said program director Tom Poleman.

"The kids were into the angst-ridden rock music for a while, but it just got too depressing," he said. "People wanted to hear something more upbeat and fun."

The flip side may be some disenfranchised males, particularly young men who like aggressive rock. "It was a horrible year for harder rock," Tower's Williams said.

Pearl Jam's new album fell flat. The testosterone-fueled Lollapalooza tour was a bust and may be abandoned this summer. Rock accounted for 46 percent of music sales a decade ago; last year, 33 percent.

Young men "aren't too sure about all this new music," Anthony said. "These are the guys who really want to rock, and when you look at the rock out there, I'm not too sure that they're being served the way they want to or need to be."

For now, at least, it's ladies' choice at the music store.