China e-commerce giant Alibaba (BABA)  can rest easy this week even as U.S. e-commerce giant Amazon (AMZN)  works hard to top last year's Prime Day record-breaking performance.

Prime Day 2016 was Amazon's biggest sales day ever and this year's version is expected to mark another sales record when the 30-hour event ends at 3 a.m. ET on July 12. 

Analysts estimated that Amazon pulled in $500 million to $600 million last year on Prime Day, although Internet Retailer estimated the figure to be as high as $1.8 billion worldwide and predicted it could rake in $2.2 billion during the 30-hour event this year. However, that's still child's play compared to the $17.8 billion in sales that Alibaba recorded during its 24-hour Singles Day event last November 11, up from $14.3 billion in 2015. 

Last year, Amazon's total revenue was $136 billion, meaning Alibaba's Singles Day event brought in about 10% of Amazon's full-year sales figure. 

Amazon's stock was trading slightly lower on Tuesday morning to $992.65 after gaining about 2% on Monday. The stock is up about 32% year-to-date. Alibaba's stock is trading up 64% year-to-date to $143.87.

Of course, Alibaba's Singles Day has had a head start. The holiday was originally celebrated in China as a sort of anti-Valentine's holiday in the 1990s before Alibaba capitalized on it in 2009 and began offering big sales to help single people celebrate being alone on November 11, or 11/11. It's a day to treat yourself, hence the massive sales on Alibaba each year, and has become a measure of how well Alibaba is doing. It's the biggest shopping day of the year in China and outperforms Cyber Monday and Black Friday's sales combined in the U.S.

Amazon's Prime Day is a much newer affair. The massive sales event was started in 2015 as a way to celebrate the company's 20th birthday. The company wasn't sure if it would continue the event past the first year, but the impressive sales results convinced them to make it an annual event. 

Alibaba also has the advantage of offering its Singles Day sale to all of its customers, while Prime Day is only open to Amazon Prime members who pay $99 per year for perks like free two-day shipping and access to free movies and TV shows to stream. A large part of Prime Day's purpose is to sign up new Amazon Prime members, who spend much more on the platform than non-Prime members. JPMorgan recently estimated that Amazon has more than 70 million Prime members worldwide. 

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