The percentage of S&P 500 companies that fired their CEO in 2014 fell to the lowest level since 2005 as the US economy continued to improve, according to the 2015 edition of CEO Succession Practices, a report released today by The Conference Board.

The study found less than 16% of all CEO turnover events reported last year by companies in the index were due to dismissal, down from 23.8% in 2013 and 29.4% in 2012.

The lower dismissal rate found this year is partly a function of the marked signals of improvement in the broader US economy, according to Matteo Tonello, managing director of corporate leadership at The Conference Board and co-author of the report.

“A softer rate was also foreseeable in light of the high turnover reported by S&P 500 companies in the last few years, when approximately one out of four departing CEOs was let go by the company board,” Tonello said.

More stable economic conditions and the improved corporate performance of the last couple of years have halted the declining trend in average CEO tenure observed by The Conference Board in the first decade of the century. In 2009, at the peak of the financial crisis, the average CEO of an S&P 500 company held his position for 7.2 years, the shortest average tenure registered by The Conference Board and down from the 11.3 years found in 2002. However, CEO tenure in large companies started to rebound soon after, rising to 8.4 years in 2011, 9.7 years in 2013, and 9.9 years in 2014 — the longest since 2002.