Jonathan Bush of AthenaHealth isn't the only CEO looking for a new job this year.

The rate of CEO turnover among American companies has increased 15% from this time last year, executive coaching firm Challenger, Gray & Christmas, Inc. reported Wednesday.

"There is uncertainty in the labor market even though the economy is doing well," Challenger, Gray & Christmas Vice President Andrew Challenger said. "The potential for new tariffs and the new tax plan coming into effect are adding uncertainty and making the labor market tight."

Since January, the CEOs of 541 American companies announced they would be leaving their posts, including Starbucks' ( (SBUX) - Get Report ) Howard Schultz who resigned Monday as executive chairman amid rumors of a presidential bid after stepping down as CEO in April. Other notable departures include Marvin Ellison's jump from J.C. Penney  (JCP) - Get Report  to Lowe's  (LOW) - Get Report  , Campbell Soup Co.'s   (CPB) - Get Report  Denise Morrison's unexpected retirement and Papa John's  (PZZA) - Get Report  founder John Schnatter's exit after criticizing the NFL's handling of players who knelt during the national anthem.

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Computer companies have seen one of the largest increases in CEO turnover, with the number of departures up 103 % from this time last year. Challenger expects this trend to continue amid growing privacy concerns in Silicon Valley. WhatsApp founder Jan Koum, left his company in April amid FaceBook's (FB) - Get Report  privacy scandal.

Bush is in a small group of CEOs brought down by the MeToo movement, as the number of CEOs who resigned in scandal this year has fallen, Challenger said. The AthenaHealth  (ATHN) - Get Report  founder, who is the nephew of former president George H.W. Bush, allegedly violently attacked his first wife and made inappropriate sexual remarks in front of female employees.

"There were less departures than people might have thought when MeToo was at its strongest last year," Challenger said. "We expected to see more departures from the business world than from Hollywood but we haven't seen that come to fruition."

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