Apple ceded its position as the world's most valuable company to Exxon Mobil as the smartphone maker's shares continue to take a nosedive.

The ranking is predicated on market capitalization, i.e. total outstanding shares multiplied by the share price. Apple shares closed down another 2.36 percent on Friday at US$439.88, bringing market to $413.1 billion.

Exxon Mobil shares by contrast rose 0.42 percent to $91.73, raising its market cap to about $5 billion more than Apple's. It was the first time in a year that Apple ceded the top spot. Exxon and Apple consistently hold the two top places.