is now worth $527.5 billion, which makes it the most valuable company in the Standard & Poor's 500, but rivals are not far behind. Apple
's revenue dropped about 12% to $50.6 billion during the quarter, the biggest drop in revenue since the third-quarter of 2001, according to data from S&P Global Market Intelligence
. But Apple
's reliance on the mature and stalling smartphone market is turning into a liability as the market gets saturated.