Fortune unveils top 500 companies of 2015

Fortune Magazine is out with its annual list of America's top 500 companies and "CBS This Morning" was first to reveal the winners.

For the third straight year, retail giant Walmart (WMT) took the top spot. It generated $486 billion in revenue in the last fiscal year, and in August, plans to raise wages for more than 100,000 of their store managers.

According to Fortune editor Alan Murray, it's a sign CEOs recognize the wage gap problem.

Behind the Fortune 500

"The amount of money that's gone to the owners of capital, to the stockholders, to the rich, basically, over the last decade while wages have been stagnant, is a problem and all of the CEOs I talk to recognize that. They know it's a big problem and they're trying to think of creative ways to deal with it without undercutting their profit, obviously," Murray said Thursday on "CBS This Morning."

While they dominate the Fortune list based on revenues, Murray says Walmart's success has not been without setbacks recently.

"What's interesting is Walmart is actually had a pretty tough patch of it for the last few years; its sales are not increasing very rapidly," he said.

Apple (AAPL) earned fifth place with an $183 billion revenue. Murray said if their list was based on market cap, Apple --valued at over $700 billion-- would be at number one.

"It's the first company ever that's had a market cap that large," he said.

Facebook has a similar story. While the company jumped from the 341st to 242nd spot, Murray said they would be number 10 if the list was based on market value.

"The market sees a lot of potential for Facebook (FB) to continue to grow so you'll probably it go up next year," he said.

Looking ahead, Murray said he sees big things in the technology sector.

"Cloud computing, mobile computer, big data, artificial intelligence - what people call the Internet of things, putting sensors on everything that goes on in the company and collecting that data is going to transform the way companies do everything, and they know about it, and frankly they're a little scared about it," he said.

This year, for the first time, Murray and Fortune polled the top 500 CEOs. He said JPMorgan Chase's Jamie Diamond and Apple's Tim Cook were the most admired.

"I don't think any of us thought that [Cook] could take Apple to the heights he has taken it," Murray said. "It really is an amazing story."