Times have been tough for big box stores with physical footprints. Several stores, including American Apparel (again), have declared bankruptcy. National chains such as Macy’s, J.C. Penney, and Sears have been closing stores and shifting resources in order to strengthen their e-commerce capabilities. But in the midst of bankruptcies and store closings, online retailers continue to gain ground.

Amazon continues to thrive and is now considered the third largest retailer in the entire world. It is ranked 83rd among the top 2000 businesses on Forbes’ list of the most powerful companies in the world. And their piece of the pie shows only opportunity to acquire more. E-commerce sales in the United States are growing by double-digit percentages each year and are expected to reach $4 trillion by 2020.

Amazon derives its revenue mostly from online sales, although the e-commerce giant has begun purchasing physical stores to establish a presence in that arena. Conversely, the top 25 retailers include many traditional brick-and-mortar companies who remain in the top bracket only because they have expanded their efforts in the online sector over the last few years. Companies that maintain a presence both in the traditional and online sectors include well known brands like Target, Macy’s, and Nordstrom.

Amazon’s phenomenal growth could be attributed to its diversification into new areas, including home goods where the company has introduced its private label, Amazon Basics. Amazon continues to snap up other online retailers, too. In addition to entering the grocery business with the acquisition of Whole Foods, it is now considering making a foray into the pharmacy industry.

Amazon has been consistently pushing the boundaries of its operations and promises to remain an overwhelmingly powerful juggernaut in the e-commerce industry.