CFOs looking for a promotion — or who simply can’t bear their CEO — may take pleasure from the latest annual survey of CEO succession from consultancy Booz & Co. Last year the proportion of top bosses who were replaced in the world’s 2,500 biggest companies rose sharply to 14.2% — that’s 355 CEOs who moved out — from 11.6% in 2010.

The improved outlook for the economy (or at least it seemed so at the time) is partly credited for the acceleration in CEO turnover. “Boards are increasingly seeking new leaders to help drive growth in a recovering global economy,” the survey authors declare. But if not a catch, there’s at least a hard bargain: the need to ride the upswing “places a distinct burden on those newly elevated CEOs to prove themselves early in their tenure.”

As José Ricardo Mendes da Silva, CEO of Brazilian group Aché Laboratórios Farmacêuticos, says in the survey: “There’s always some sort of crisis in the CEO’s first year — something that probably led the former CEO to leave — and it is key to initially focus exactly on the issues related to that crisis.”

Overall, 2.2% of CEOs lost their job because of mergers and acquisitions activity (a less-common reason for departure in the largest, most-impenetrable 250 companies), 9.8% were “planned” departures, and the remaining 2.2% were forced out for other reasons.

Good news for CFOs with their eye on the CEO role: so-called insider CEOs — those promoted from within the company rather than appointed from outside — serve longer and, more importantly, create more value for shareholders with a 2009–11 performance that beat local market indices by 4.4% (compared with 0.5% for external CEOs). Better still, insiders are about half as likely to be forced out of the company than outsiders are.

The bad news: those insider promotions are harder to get. In 2011, 22% of CEOs were external appointments, compared with just 14% back in 2007.

Geographically, the turnover rate was a little higher in Western Europe (13.9%) than in the United States (13.5%), but it was 16.8% in Japan and 22% in Brazil/Russia/India (taken together). In the fourth BRIC, China, the CEO turnover rate was just 6.8%.

The Booz survey makes no mention of the role of CFOs in succession planning. It does, however, carry advice to newly appointed CEOs from Andre-Michel Ballester, CEO of the Italian company Sorin Group: “The first issue is to create a leadership team very quickly, making decisions on who are the keepers and who are the leavers in the first few weeks.”

And therein lies the sting in the tail: CFOs who wave goodbye to their CEO but who don’t get the top job themselves should quickly cement their relationship with the successful CEO candidate. In fact, recent research by recruiting firm Korn/Ferry suggests that 28% of CFOs leave their company within two years of an external CEO’s appointment. If another internal candidate gets the CEO role, there is only a 10% chance the CFO will leave for new pastures.

That may not be surprising: an incoming CEO may well want to make sure he has his preferred executive team around him without having to battle against the ingrained attitudes of C-suite officers who worked with the previous CEO. But while the appointment of an external CEO creates an opportunity for a CFO to prove what a critical role he plays — and can continue to play — it’s probably easier to convince an internally promoted candidate who is already familiar with what the CFO can do.

Andrew Sawers is editor of CFO European Briefing, a CFO online publication.