Larry Page, co-founder and chief executive officer at Google, speaks here at the Google I/O Annual Developers Conference in San Francisco, California, on May 15, 2013. Photographer: David Paul Morris/Bloomberg

Who are the very best CEOs?

According to Barron's, which creates its own list using metrics like investor returns and leaders' innovation track records, Under Armour's Kevin Plank and Walt Disney's Robert Iger are among the top.

According to Harvard Business Review, which measures long-term shareholder return over an entire CEO's tenure, last year the best was Amazon's Jeff Bezos (who also owns the Washington Post).

And according to Fortune, the accolade goes to Apple's Tim Cook.

But who would employees rank as the best CEOs? According to career Web site Glassdoor, which released its annual ranking Tuesday night, the top three favorites among employees at large companies are Google's Larry Page, Nike's Mark Parker and H-E-B's Charles Butt, who founded the Texas-based grocery chain.

Those CEOs received the highest ratings from their employees, who provided anonymous company reviews on Glassdoor's site. Also in the top 10 are Facebook's Mark Zuckerberg (No. 4), Monsanto's Hugh Grant (No. 6) and Goldman Sachs' Lloyd Blankfein (No. 7).

This year's list appears to indicate a possible increase in overall employee satisfaction with companies' leadership from last year.

Whereas No. 50 on last year's list, General Electric's Jeffrey Immelt, had a 78 percent approval rating, this year's No. 50, Marriott's Arne Sorenson, beat that by 10 percentage points. One explanation could be that employees are by and large happier given the improving job market.

"We know the economy is bouncing back, and this is freeing up companies and leaders to provide additional benefits," said Scott Dobroski, Glassdoor's community expert.

But making year-over-year comparisons is a tricky exercise. For one, the difference in satisfaction with the highest-ranked leaders on the list and those that just squeak above No. 50 is pretty marginal. There's a difference of just nine percentage points between Google's Page (97 percent) and Marriott's Sorenson (88 percent). So falling or rising a few spots may not mean terribly much.

Moreover, the pool of companies considered for the ranking grew substantially between 2014 and 2015, from 120,000 to 180,000. For companies with more than 1,000 employees, it takes at least 1oo reviews to be considered. For smaller firms, it takes at least 35 reviews.

That could help explain why there was big turnover on the list, Dobroski said. For instance, some CEOs who ranked highly this year — such as Parker at Nike — weren't eligible for the list last year because they didn't have enough reviews.

The influx of new entrants might also explain some of the drops in ratings. Starbucks CEO Howard Schultz, for instance, had a 93 percent approval rating last year and ranked eighth. This year, he fell to 31st, though his approval rating dropped only slightly, to 91 percent.

Could public relations types be filling the site with glowing reviews of their CEOs? Dobroski said it's possible, but said Glassdoor verifies anonymous reviews to the best of its ability, trying to stamp out fraudulent reviews via technological checks as well as human reviewers. When it finds cases of companies incentivizing reviews, he said, they take them down and exclude companies from the ranking if they find evidence of anyone trying to game the system.

Here's the full list:

(Image provided by Glassdoor)

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