Amazon.com (AMZN) - Get Report is eating other retailers' lunch when it comes to online sales, with the virtual behemoth now accounting for more than a third of all online retail transactions in the U.S., though that part of its business is only a fraction of what it currently has its sights on.

According to a report published Tuesday by research and analysis provider Digital Commerce 360 Research, Amazon now accounts for 37% of all online retail sales transactions, up from 34% in 2017. Nearly 60% of Amazon's $232.9 billion revenue now comes from its marketplace, making it the No. 1 online retailer in the U.S., according to the 77-page report.

More than 25,000 sellers globally sold more than $1 million on Amazon last year alone, with the average U.S. marketplace merchant selling more than $90,000 on the site, according to the study's findings.

The study pointed to Amazon's growing fulfillment operations -- its portfolio of warehouses across the U.S. which now total some 155.4 million square feet -- as well as its investments in airplanes, with its fleet of package-shipping jets now at 50 and climbing fast.

In late June, Amazon announced a new "Delivery Service Partners " program in an effort to attract entrepreneurs who can create their own local delivery networks with up to 40 vans each. It also debuted a new delivery drone in early June, which it hopes will eventually speed up delivery for its North American Prime members.

The company has also been beefing up its advertising business. Amazon is now the third-largest digital advertising platform in the U.S. behind Facebook (FB) - Get Report and Alphabet's (GOOGL) - Get Report Google, according to the study. It has also bolstered its might in web services and even in the real-world brick-and-mortar realm.

Image placeholder title

Amazon also has been been boosting its physical retail locations including Whole Foods and Amazon Go outlets, which generated three times more revenue last year than the year before, according to the report.

And that's not to mention the company's ongoing forays into electronics, entertainment and even news.

"Assuming Amazon's efforts have these long-term effects, they'll yield additional revenue that the company could potentially use to invest more in its infrastructure and/or roll out new services," TheStreet.com's Eric Jhonsa wrote in an overview of the company.

"In other words, greater scale would help beget more scale. It's an old story for Jeff Bezos' firm."

Amazon is a holding in Jim Cramer'sAction Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells AMZN? Learn more now.