Crop tops take center stage in New York

Crop tops take over New York Fashion Week
Crop tops take over New York Fashion Week

It's official: The crop top is quickly becoming a wardrobe staple for young American women.

Just halfway through New York Fashion Week, the look has already popped up on the runway at Tommy Hilfiger, Victoria Beckham, Altuzarra, Milly, Carmen Marc Valvo and a slew of other shows.

"Everyone do your abs," Milly designer Michelle Smith joked backstage ahead of her show.

A model walks the runway during the Milly show in New York during Fashion Week on Sept. 9, 2016.
Adam Jeffery | CNBC

Yet as the look becomes more popular — thanks to the influence of athleticwear, a resurgence of '90s style and a more widespread adoption of bralettes — it's taking on various forms, said Lizzy Bowring, head of catwalks at WGSN, a trend forecasting firm.

A model walks the runway at Altuzarra during New York Fashion Week at Spring Studios on Sept. 11, 2016, in New York City.
Antonio de Moraes Barros Filho | FilmMagic | Getty Images

While these midriff-baring tops were shown as tiny ruffled pieces at Altuzarra, they had a sportier take at Tommy Hilfiger. And at Carmen Marc Valvo, there was a more conservative spin on the trend, which showed just a hint of the model's stomach. That makes the item more wearable.

"It doesn't have to be a bralette or a little bandeau. It can be a longer-lying crop top," Bowring said.

A model walks the runway at the Carmen Marc Valvo fashion show in New York on Sept. 11, 2016.
Adam Jeffery | CNBC

Bralettes, a lightweight take on the traditional bra, have been a big hit for retailers. The item contributed to a 24 percent same-store sales increase at American Eagle's aerie lingerie label last quarter.

Bralettes' popularity bodes well for retailers' revenues, as they're often paired with off-the-shoulder or sheer tops. That means shoppers are tempted to scoop up additional items with their purchase.

Data from WGSN Instock, an online analytics system, recorded a 60 percent year-over-year increase in the amount of bralettes arriving at U.S. online retailers between February and June.

Cropped styles accounted for 7 percent of new tops during that period, compared with 8 percent the previous year.

Kendall Jenner walks the runway at the Alexander Wang fashion show during New York Fashion Week at Pier 94 on Sept. 10, 2016, in New York City.
Presley Ann | Patrick McMullan | Getty Images

Other trends emerging on the New York runways include what WGSN is calling "purity." That look incorporates "luminous whites" and lots of cottons and linens, Bowring said. Another theme is "refined deconstruction," a technique that helps the clothes define the female form. That was seen at Prabal Gurung, Victoria Beckham and Monse, Bowring said.

"That plays into all the beautiful femininity that we're seeing," she added.

A model displays the fashion of Nicholas K during New York Fashion Week on Sept. 8, 2016.
Angela Weiss | AFP | Getty Images

Yet that doesn't mean athletic-inspired looks are going away. At Carmen Marc Valvo, for example, models paired sneakers with feminine dresses.

"That sport influence is incredible. How many seasons do we keep seeing it?" Bowring said. "It's part and parcel of the American lifestyle."