Ballmer to leave Microsoft within a year Microsoft said that Steve Ballmer would retire as its chief executive within 12 months, sending shares in the world's largest software company by market capitalisation up by as much as 8.7 per cent. Bill Gates, Microsoft's founder and chairman, will form part of the board's succession planning committee to find his replacement. The departure will end Mr Ballmer's 13-year tenure as chief of the software company and make him the highest-profile casualty yet of the post-PC era ushered in by Apple and Google's mobile devices. Mr Ballmer, who joined Microsoft in 1980, has come under pressure in recent months after problems with Windows 8, an attempt to make an operating system that spans both the PC and the tablet devices. Microsoft stock has lost around 40 per cent of its value since Mr Ballmer assumed the chief executive position in January 2000. The company's shares rallied in the first five months of 2013, but suffered a steep decline in mid-July after a poor earnings report. "There is never a perfect time for this type of transition, but now is the right time," Mr Ballmer said. We have embarked on a new strategy with a new organisation and we have an amazing senior leadership team. My original thoughts on timing would have had my retirement happen in the middle of our company's transformation to a devices and services company. We need a CEO who will be here longer term for this new direction. Earlier this year, Microsoft said it would break its eight business lines up in favour of four new segments to focus on engineering and to better encourage collaboration across the company. The divisions are expected to focus on operating systems, apps, cloud technology, and devices. There is never a perfect time for this type of transition, but now is the right time Steve Ballmer, Microsoft outgoing chief executive The move largely reversed the strategy and structure put in place by Mr Ballmer in 2005. In an email to staff released by Microsoft, Mr Ballmer said that he was "proud of what we have achieved," after seeing the company rise from $7.5m in revenues and 30 employees to $78bn and 100,000 staff today. "We have more than 1bn users and earn a great profit for our shareholders," he said. We have delivered more profit and cash return to shareholders than virtually any other company in history. Nonetheless, analysts at Gartner have predicted that Apple's share of the consumer device market, including PCs, smartphones and tablets, will overtake Microsoft's this year, underscoring the struggle that Windows faces for relevance in the mobile era. In July, Microsoft said that it saw a 20 per cent drop in consumer demand for PCs and took a $900m inventory writedown for its struggling Surface RT tablet.. According to IDC, Windows Mobile held a 3.7 per cent market share of the smartphone market in the second quarter of 2013, compared with Google Android's 79.3 per cent. After initially trading as high as $35.20, Microsoft's shares eased back in late morning trading to be 6.3 per cent higher at $34.44.