There were 24 CEO changes in the health sector, amounting to 95 total departures this year, so far.
Government/nonprofit institutions announced the second highest number of CEO changes with 13.
Financial firms had 10 departures while the computer sector had nine.
All told, 36 CEOs cited resignation as their reason for departing, 21 retired from their posts, while 14 stepped down into other roles within the executive leadership ranks, usually as a chairman.
The remaining executives either found new jobs or had their interim role end.
One of the most notable departures in May was the sudden retirement of 59-year-old Bob McDonald, who headed global consumer products company Proctor & Gamble for four years.
While the official reason was retirement, it was widely reported that McDonald’s exit was prompted by increasing pressure from investors.
“The fact that this 33-year company insider was forced out after just four years in the CEO position is a clear indication of how much more power and influence shareholders have in the direction of a company," said John Challenger, chief executive of Challenger.
"Boards really can no longer simply be rubber stamps or ‘yes men.’ In this environment, no CEO is secure,” he said.