Equal Pay Day, which occurred on Tuesday, highlights how much of a salary gap still exists between men and women in the workplace. But at least a few female CEOs aren't having trouble earning their worth.

A USA Today analysis reported Wednesday morning shows that the highest-paid female CEO, among companies that have released their proxy since the start of the year, is Lockheed Martin's Marillyn Hewson. The chief executive of the aerospace and defense giant saw her total pay package for 2014 grow to $33.7 million, according to the company's proxy.

In terms of total compensation, that puts her at the top of all female CEOs in the Standard & Poor's 500-stock index that have filed so far. In addition, according to USA Today's analysis, it makes her the only woman among the top 10 CEO earners, again for companies that have already released their data.

A company spokesperson declined to comment further about Hewson's compensation, but as USA Today noted, investors probably won't raise too many concerns. Lockheed Martin's stock rose some 30 percent in 2014, far better than the S&P 500.

Notably, a few companies with female CEOs have yet to file their data this year, including Yahoo, General Motors and Oracle. We do have a sense of what they're likely to pay, though, based on previous figures. Yahoo filed its proxy last year in late April, which showed that CEO Marissa Mayer made $24.9 million in 2013. GM said early last year that Mary Barra would make about $14.4 million in 2014. And Oracle's Safra Catz, who was named co-CEO in September and made more than $37 million as president in the company's last fiscal year, could eventually top Hewson's pay.

Among companies that already have filed proxies this calendar year, the next two highest-paid female CEOs after Hewson are PepsiCo's Indra Nooyi, whose total compensation for 2014 was valued at $22.5 million and Xerox's Ursula Burns, whose was valued at $22.2 million. Such numbers reflect what CEOs stand to make, but not necessarily their annual take-home pay.

The big boost in Hewson's 2014 compensation came from a change in her pension value, which rose by nearly $16 million — or nearly half of her total pay package. The difference was big enough that Lockheed, like a growing number of companies, created a separate column in the company's pay table for the amount she earned without the pension value change, which was "only" $17.9 million.

Yet while companies may want to separate those numbers, investors tend to think the whole picture is more valuable, said John Roe, executive director of ISS Corporate Solutions. "Many institutional investors think the change in pension should be included, because it includes a real cash payout CEOs will take with them when they retire," he said in an interview with The Post.

Hewson's not the only one to see her pension value shift significantly this year. Due to changes in the actuarial tables for CEOs' life expectancies, as well as continued low interest rates, this is proving to be the "largest pension adjustment year in the history of executive pay since disclosures were required in 2006," Roe said. Within at least 15 companies this year, he said, the change in pension value was actually greater than all the other elements of the CEO's pay combined.

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