Janet Robinson, chief executive at The New York Times and the first woman to become president and CEO of the The Times company, is quitting the paper, and both those within the company and without are scratching their heads as to why.

As the company continues to struggle with a years-long slump in share prices and fights to keep subscribers, Robinson's exit after seven years at The Times Co. has caught both outside analysts and company insiders completely by surprise.

Robinson's tenure, while rocky, has had many impressive successes to its name, and her departure comes with no preparation or replacement waiting in the wings. All of which begs the question: Why is Janet Robinson stepping down?

First Woman to Head New York Times

When Janet Robinson became the first woman to head The Times Co. in 2004, she entered at a crucial crossroads in the newspaper industry, one in which print newspapers prepared to spend the next decade finding a new and at times awkward compromise between old and new media.

Though Robinson, 61, did much to broaden the company's national reach and increase revenue from new initiatives online, her tenure also saw The New York Times slashing staff as print advertising revenue took a steep dive and the company itself teetered into debt.

And while fellow company papers The Boston Globe and The International Herald Tribune were saved from being axed, The Times Co. had to sell most of its midtown Manhattan headquarters in 2009 to raise cash, and even borrowed money from Mexican billionaire Carlos Slim at steep interest rates in order to make ends meet.

In all, however, Robinson remained a largely positive and pioneering figure in the journalism industry during her 28 years at The Times, making her departure all the more shocking.

Could Stock Prices Be Reason for Robinson's Exit?

The Times Co. gave no explanation for Janet Robinson's abrupt departure, and Robinson herself gave no prior notice before the announcement that she would step down yesterday.

Even more unusual is the fact that her resignation comes just as Martin Nisenholtz, the company's longtime digital leader, announced his own resignation. Although publisher Arthur Sulzberger Jr. plans to oversee the company in the short-time, Robinson and Nisenholtz's joint departures mean that The Times Co. will enter 2012 without a CEO, long-term president or digital boss.

As analysts and insiders continue to scratch their heads over Robinson's unexpected exit, however, some have already begun to speculate that the CEO, who had been with The Times for 28 years, had been undone by bad stock numbers and was pressured to step down.

It is very unusual to have a long-time CEO suddenly announce her leaving within two weeks with no replacement, Evercore Partners analyst Douglas Arthur told Reuters. She's done a lot of good things, but at the end of the day the stock price is the ultimate measure of success.

On that count, at least, The Times Co.'s performance over the past decade has been sorely lacking.

Times stock has declined by more than 80 percent since Robinson became CEO in December 2004, and 2011 alone saw shares drop by nearly 25 percent. On Dec. 15, shares were at $7.53, when they had been as high as the mid-$30s during Robinson's earlier years.

The idea that Robinson may have been pressured to leave is supported by the fact that even the CEO herself appeared to have made no plans to exit only a few days before her announcement.

No one had an inkling this was coming, said a source at The New York Times. As recently as last week she was taking meetings with people and mapping out business plans for well into next year.

Getting Out Now: 'Print Advertising is in a death spiral.'

Even as some speculate that Janet Robinson is bowing to pressure brought on by low stocks, however, other remains skeptical that the decision was about the company's performance during her tenure, citing her impressive accomplishments in spite of all the obstacles thrown her way.

Although Robinson's attempts to monetize online media could be hit or miss (as with the ill-conceived Times Select program some years earlier), the CEO is rightfully credited with lowering paper costs, dominating Internet-focused media and re-establishing The New York Times as the premier paper to read, either in print or online.

The Times currently ranks just below rival The Wall Street Journal as the top in digital subscribers and third behind WSJ and USA Today in print subscribers, a very impressive ranking as many papers continue to go under.

Despite its recent gains, however, there is little chance that The New York Time's annual revenue will greatly improve in 2012, and it could be that Robinson is simply calling it quits while her influence is still felt.

The headaches aren't over because print advertising is in a death spiral, newspaper analyst Ken Doctor said. The New York Times is ahead of the curve digitally, but there are still some blind turns ahead. Their future is still not secure.

Robinson Expresses 'Mixed Emotions'

In the end, only Robinson herself is likely to offer a full explanation, and so far the former CEO and president is keeping mum.

Obviously, the last few years have been tough as, together, we have navigated one of the most difficult periods in publishing history, Robinson said in a staff-wide memo.

She expressed pride at having navigated the paper from traditional print journalism into the uncertain waters of new media, and said she was leaving the company with mixed emotions. In her closing statements, she assured her former co-workers that a system was in place that would serve the company well for many years into the future.

Robinson will serve as a consultant for one more year, according to The Washington Post. She will be paid $4.5 million in 2012.

Robinson Praised for Vision as Times Seeks Replacement

As questions about Janet Robinson's abrupt departure continue to hand in the air, published and interim CEO Sulzberger took the opportunity to praise her for her accomplishments at The Times Co., saying the nearly three decades of work Robinson contributed to the company helped make The New York Times a truly national newspaper.

It took huge coverage and vision on Janet's part to create and to successfully implement out national edition, he said in a staff memo. We will always be in her debt.

As Sulzberger serves interim CEO, however, the next burning question is who will take over as head of the company, and Arthur thinks the paper may look outside for her replacement.

My view is that they should find someone from outside, the Evercore analyst said. This is a very challenged industry undergoing a wrenching transformation and I think a strong outside candidate will be positive for the stock and for their strategy.