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Amazon has shown no sign of slowing down in recent years, expanding into areas such as cloud computing, logistics and most recently, firmly entrenching itself in the $800 billion grocery market with its acquisition of Whole Foods.

But one area where the company has fallen short over the past nine years?

Income taxes.

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According to a new post from NYU marketing professor Scott Galloway, Amazon has paid just $1.4 billion in income taxes, compared to $64 billion for its chief competitor, Walmart. During the same time frame, Walmart has generated $229 billion in profit, before taxes and dividends were paid to shareholders. Amazon on the other hand, has generated $14 billion in profit.

Galloway poses that this may be an issue.

"The most uncomfortable question in business, in my view, is how do we pay our soldiers, firefighters, and teachers if a firm can ascend to $460 billion in value (#5 in the world) without paying any meaningful corporate taxes," Galloway wrote in the post.

Galloway is renowned for his marketing acumen and having accurately predicted that Amazon would buy Whole Foods.

Investors have rewarded Amazon, sending its stock up more than 17 times since the start of 2009, according to data compiled by Google Finance. Excluding dividends, Walmart's shares have risen by approximately 30 percent  during the same time frame, severely underperforming the S&P 500.

Pressure from Trump

Amazon has come under fire from President Trump in recent months, first on the campaign trail and since entering office.

In Feb. 2016, Trump said that Amazon would have problems if he became President.

"He [Jeff Bezos] wants political influence so that Amazon will benefit from it," Trump said, according to CNET. "That's not right. And believe me, if I become president, oh, do they have problems. They're going to have such problems."

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Since becoming President, Trump has gone after Amazon a number of times, for different reasons.

In June, he went after the company, claiming that it does not pay "internet taxes," though it is unclear what he meant by "internet taxes." In July, Trump said the e-commerce giant is "doing great damage" to retailers, forcing several of them, including companies such as Macy's, to close stores around the country.

Follow Chris Ciaccia on Twitter @Chris_Ciaccia