NEW YORK (CNNMoney) -- Four longtime Yahoo board members, including the chairman, are leaving the company.
Chairman Roy Bostock announced the shakeup -- including his own departure -- in a letter addressed to shareholders late Tuesday. The other exiting board members are Vyomesh Joshi, Arthur Kern and Gary Wilson.
The four directors will not seek re-election at the next Yahoo (YHOO, Fortune 500) shareholders' meeting, which has not yet been scheduled but is typically held sometime in the spring.
The departures stemmed from board discussions about "why Yahoo! was not meeting either our own expectations or those of our shareholders," Bostock wrote.
That's putting a kind spin on things. Critics have called for the board directors' heads as Yahoo struggles to reinvent itself. The company gave up on search in 2009, and it's losing ground in display advertising to new entrants to the market such as Google (GOOG, Fortune 500) and Facebook.
Yahoo's leadership has struggled as well. Bostock himself famously fired Yahoo CEO Carol Bartz was via phone in September. Four months later, Yahoo named Scott Thompson as its new CEO. Thompson was previously the president of PayPal, an eBay subsidiary.
Thompson's hiring was one outcome of an analysis that began six months ago, according to Bostock's letter, and was kicked off during a special meeting of Yahoo's independent directors -- meaning that then-CEO Bartz didn't attend.
The group decided to "move aggressively on three fronts": finding a new CEO, reviewing Yahoo's strategy and structure, and reconsidering the company's board composition. This week's board departures are a result of that scrutiny.
Last month, Yahoo co-founder Jerry Yang resigned his board post and all other positions at the company.
Yahoo has already named two new board members: Alfred Amoroso, previously of Rovi Corporation, and Maynard Webb, Jr., formerly an executive at eBay (EBAY, Fortune 500) and Gateway. A search for "additional" new directors continues.
After the four officially leave their posts, the majority of Yahoo's board will have joined the board in 2012. All nine will have joined since 2010.
That should please critics who have called for an infusion of fresh blood at Yahoo board. But it's unclear whether the board shakeup will clear a path to a Yahoo sale, another option some vocal shareholders have pushed.
Yahoo's board has talked with potential investors over the past few months and reviewed several equity investment proposals, but so far, it is unimpressed, according to Bostock's letter.
"There have not been any proposals which have been deemed by the committee to be attractive to our shareholders," he wrote. 
