NEW YORK (AP) — Amazon's Jeff Bezos challenged other retailers to raise wages and improve benefits for their employees, saying the competition will help everyone.

Bezos covered a wide range of topics in his annual letter to shareholders Thursday that was released on Twitter and filed with the Securities and Exchange Commission .

"Today I challenge our top retail competitors (you know who you are!) to match our employee benefits and our $15 minimum wage," Bezos wrote. "Do it! Better yet, go to $16 and throw the gauntlet back at us."

In response, Dan Bartlett, a top spokesman for Walmart, fired a jab against Amazon on Twitter , referring to the fight with states about how taxes are collected. Bartlett cited a report from the Institute on Taxation and Economic Policy that noted Amazon will pay nothing in federal income taxes for the second straight year.

"Hey retail competitors out there (You know who you are) How about paying your taxes?" Bartlett tweeted.

Late last year, Amazon jumped ahead of many rivals by raising its minimum wage for U.S. workers to $15 an hour. That pay hike was not universally praised by all workers, who said the company cut two employee benefits as well: monthly bonuses and the chance to own some of Amazon's sky-rocketing stock.

Amazon did make some adjustments afterward to ensure workers were getting a raise.

Target and Walmart have increased starting wages for workers over the past few years as the job market grew hotter and people could find better pay and benefits elsewhere. Target Corp. said last week it would raise the minimum hourly wage by a dollar in June to $13 per hour, the third pay hike in less than two years.

The Minneapolis retailer has said it plans to raise starting hourly wages to $15 by the end of 2020.

Walmart, based in Bentonville, Arkansas, raised its starting pay to $11 an hour in early 2018.

And it appears Amazon, well-known for giving low priority to the short-term growth interests of Wall Street, will continue taking big risks if it sees a potential pay-off in the long run.

In his letter Thursday, Bezos said Amazon's Fire phone was a failure, but that its Echo and Alexa smart speakers have been tremendously successful.

"As a company grows, everything needs to scale, including the size of your failed experiments," Bezos wrote. "If the size of your failures isn't growing, you're not going to be inventing at a size that can actually move the needle. Amazon will be experimenting at the right scale for a company of our size if we occasionally have multibillion-dollar failures."

Bezos said one "big winning bet" can cover the cost of the clunkers, and that calculus has been playing out at Amazon.

Amazon churned out profits last year that exceeded $10 billion, more than tripling net income from the previous year.

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