For the first time, online retailers are starting to dominate market share in the S&P 500 consumer discretionary index over traditional bricks-and-mortar, proving what we all know: the industry is in serious transition.

Online retailers now comprise 22% of the index's market cap, compared to 10 years ago when they held a mere 2.5%. Amazon (AMZN) - Get Report , the e-commerce giant blamed for many recent traditional retailer's Chapter 11 filings, alone makes up 16.8% of the index's sector, versus the 1.4% 10 years ago, according to Bloomberg data.

The consumer discretionary's market cap has nearly doubled in the past decade to $2.7 trillion.

For traditional bricks-and-mortar retailers, this is not good news. Several major mall-based retailers including Macy's (M) - Get Report , J.C. Penney (JCP) - Get Report and the dyingSears Holdings Corp. (SHLD) have been forced to shutter massive amounts of stores, and others have been filing for Chapter 11 protection in droves as they lose customers to e-commerce.

On Tuesday, teen specialty retailer Rue21 became the latest to succumb to bankruptcy, filing in the Western District of Pennsylvania with a restructuring support agreement to scale down its debt from lenders holding 96.8% of its secured term loan, bondholders holding 60.2% of its outstanding unsecured notes and its majority shareholder. Under its proposed reorganization plan, the debtor will give its term loan lenders, owed $521 million, 96% of reorganized equity.

Rue21 is requesting that the court approve its motion to close up to 400, and no less than 396, of its 1,179 stores across 48 states, and said it hopes to emerge from Chapter 11 as a "more focused and highly performing retailer." The company said it may opt to shutter more stores throughout its case. The liquidation process at 396 underperforming Rue21 stores began on April 14 and is expected to yield $37 million in net proceeds.

The retailer also obtained up to $125 million in debtor-in-possession financing from its existing ABL lenders, and up to $50 million in new money from its term loan lenders.

"These actions are being undertaken with the goal of strengthening the company's balance sheet, achieving a more efficient cost structure and concentrating resources on a tighter retail footprint in order to pave the best path forward for rue21," Company CEO Melanie Cox said in a statement.

The company's filing comes behind several other retailers looking to scale down their debt and store footprint in Chapter 11, amid the heightened pressures on the industry, which include dwindling mall traffic, the rising cost of wages and rent and the increased pressure from e-commerce.

On April 28, specialty menswear retailer B&B Bachrach filed for bankruptcy, following in the footsteps of discount shoe store chain Payless ShoeSource, Gordmans Stores (GMAN) - Get Report , sporting goods retailer Gander Mountain, RadioShack successor General Wireless Operations, appliances, electronics and furniture retailer HHgregg and ready-to-wear products designer and seller BCBG Max Azria Global Holdings.

Read More Trending Articles:

Editor's Pick: Originally published May 16.