The percentage of S&P 500 companies that fired their CEO in 2013 was the lowest since 2010, according to the 2014 edition of CEO Succession Practices, a report released Wednesday by The Conference Board.

The study found that 23.8 percent of all CEO turnover events reported last year by companies in the index were due to dismissal, down from 24 percent recorded in 2010 and 25.5 percent in 2011. As a result, CEO tenure grew in 2013 to 9.7 years, reversing a decade-long declining trend.

“Our research shows that, following years of exceptional scrutiny of CEO performance, the witch hunt is over and senior management is finally getting a break. It is happening because the stock market has been faring so well, shareholders are happy and directors feel less pressure to bring change quickly and at all costs,” said Matteo Tonello, managing director of corporate leadership at The Conference Board and coauthor of the report. “On many levels, this is welcoming news, as it means that the relationship between boards and CEOs is relieved of the tension it suffered during the long years of the financial crisis.”

However, Tonello expressed concern that a  false sense of security may lead boards to reduce their commitment to succession planning and leadership development.

“The next crisis could be around the corner, the market won’t always be bullish and CEO performance should anyway be about much more than stock prices,” Tonello said. “Being prepared for a change of leadership should always be a top priority for directors, irrespective of the confidence in the moment.”