Apple CEO Tim Cook's approval rating fell in the last 12 months, dropping Steve Jobs' successor to the 18th spot on an annual ranking of American chief executives. Cook received an average approval rating of 93 percent from more than 640 Apple workers on Glassdoor, an online jobs and careers website, between March 2012 and March 2013. That put Cook at No. 18, behind several other technology CEOs such as Facebook's Mark Zuckerberg (No. 1), EMC's Joe Tucci (No. 7), Google's Larry Page (No. 11) and Amazon's Jeff Bezos (No. 16).