Shares of Starbucks Corp. sank 1.4% in premarket trade Thursday, after the coffee seller said Chief Financial Officer Scott Maw is retiring, effective Nov. 30, after about 4 1/2 years in the role. The company has launched a external search for a new CFO. Maw had joined Starbucks in 2011 as global controller, and was promoted to CFO in February 2014. Just prior to the CFO announcement, the stock was up less than 0.1% in premarket trade. Earlier this month, executive chairman Howard Schultz said he was stepping down. The stock has shed 13% year to date through Wednesday, while the S&P 500 has gained 1%.