Amazon's fast-growing apparel business should terrify Macy's and JC Penney

New survey data from Morgan Stanley suggests Amazon's fashion business is quickly growing in popularity while eating into the market traditionally owned by big box retailers like Macy's and JC Penney.

The survey, which polled 2,000 US teens and adults, says 58% of the respondents shopped at Amazon in the past six months, making it the most popular apparel retailer in the country.

Kohl's, JC Penney, and Macy's trailed by a wide margin, each receiving 37%, 33%, and 27% of the votes, respectively. The three retailers also saw the biggest declines in year-over-year purchasing activity.

"These data points continue to support our thesis that Amazon is quickly gaining consumer traction in apparel at the expense of department stores and select specialty retailers," Morgan Stanley wrote in the note Tuesday.

Morgan Stanley also forecasts Amazon will account for roughly 17% of the US apparel market by 2020, selling ~$51 billion worth of clothing items per year.

Here's a chart that shows shopping activities in the last six months:

This is the chart that shows year-over-year change in shopping activity (Amazon's not included because it's the first year included in the survey):

All of this is contributing to Amazon's growing brand awareness in this space. Amazon saw a whopping positive 47% net promoter score, a proxy for gauging brand value, while Macy's and Kohl's saw the greatest year-over-year declines.

Disclosure: Jeff Bezos is an investor in Business Insider through hispersonal investment company Bezos Expeditions.