The strong just keep getting stronger.

Amazon Inc. (AMZN) shares were marked sharply higher Thursday after the online retailing giant said membership in its lucrative Prime offering topped 100 million as it continues to expand overseas and challenge traditional retails in the world's biggest markets.

In his annual letter to shareholders, Amazon CEO Jeff Bezos said more than 5 billion packages had been shipped via Prime worldwide after a record year for new subscribers in 2017. Bezos also noted that around half of its global sales took place on Amazon Marketplace and that it's lucrative Amazon Prime Day saw 60% growth - with topline sale of 40 million items - from 2016. He also highlighted the company's  recent accomplishment of receiving top honors in the American Customer Satisfaction Index, a position its held for eight consecutive years

"The high standards our leaders strive for have served us well," Bezos said. "And while I certainly can't do a handstand myself, I'm extremely proud to share some of the milestones we hit last year, each of which represents the fruition of many years of collective effort. We take none of them for granted."

Action Alerts PLUS holding Amazon traded 1.87% higher in pre-market dealing in New York Thursday, indicating an opening bell price of $1,556.41 each, the highest in nearly a month, in a move that would extend the stock's year-to-date gain past 33% and value the group at $710 billion.

Investors are likely to welcome any detail related to Amazon's lucrative Prime division, whose members are driving the lion's share of the company's $60 billion in record fourth quarter sales published in February. Around 4 million new members signed up in the three months ending in December, the company said in it last earnings release, generating $3.2 billion in subscription fees alone. 

However, the Seattle-Washington-based group has courted controversy of late as it takes on rivals in myriad business sectors such as grocery retailing and healthcare while drawing the ire of President Donald Trump for what has called the exploitative treatment of the U.S. Postal Service.

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