In an uncertain business environment, American companies are shaking up their management.

A record number of CEOs left their jobs last quarter, according to a report released Wednesday by job placement firm Challenger, Gray & Christmas. The number who departed their posts in 2018 is the highest annual total since 2008, when the financial crisis hit.

The high level of departures is in part because companies are concerned about the outlook for the economy and markets, according to Andrew Challenger, the firm’s vice president. The job market remains very strong, but the stock market is rocky, and many economists predict a recession is around the corner.

Trade concerns hang over a number of industries, including the manufacturing and tech sectors, Challenger added.

“Boards are anticipating a changing environment and putting leadership in place who are capable of succeeding in it,” he said.

In the final three months of 2018, American companies changed 425 CEOs, according to the report. That’s almost 45% higher than the 294 US CEOs who left in the final quarter of 2017. It’s the highest quarterly total since the firm started keeping tabs in 2002.

More 1,450 US CEOs left their jobs last year, the report said — marking a 25% jump compared to 2017.

High profile departures include John Flannery, the former CEO of General Electric (GE), and Margo Georgiadis, who left toymaker Mattel (MAT) in April.

The firm also noted corporate boards are strictly enforcing company policies on personal relationships and ethics issues.

Eight CEOs left amid sexual misconduct allegations in 2018, and another four left due to allegations of professional misconduct, it said.

For example, Brian Krzanich, the former CEO of Intel (INTC), resigned in June after the company learned of a “past consensual relationship with an Intel employee.”

Challenger, Gray & Christmas relies on SEC filings, company press releases and news reports to tally executive changes. It looks at American companies that have been in business for at least two years.