Apple stock prices exceeded the $600 billion mark on Wednesday, only a month after reaching $500 billion. The only other company to reach the $600 billion mark was Microsoft in 1999, which is now valued at $260 billion.

The rise in value is particularly significant as stocks continued to fall on the main exchanges due to high US unemployment and the European debt crisis. The stock price peaked at $644 in the morning and stabilised at $629 by midday.

It has been speculated that the surge in value is down to Apple’s recent announcement that it will be using $200 billion pay a dividend and buy back some shares. Apple’s stock price has climbed 59 percent this year and a range of analysts have even said the stock has been under-valued by the market.