(File image) Katie Holmes and Tom Cruise

New York - Prince William and his wife Catherine will stay married, but don't necessarily bet on Tom Cruise and Katie Holmes managing the same thing - not according to an updated celebrity marriage formula.

Created in 2006 by scientist Garth Sundem, the Sundem/Tierney Unified Celebrity Theory is surprisingly accurate, the New York Times reported on Tuesday.

The equation takes into account the “relative fame of the husband and wife, their ages, the length of their courtship, their marital history, and the sex-symbol factor (determined by looking at the woman's first five Google hits and counting how many show her in skimpy attire, or no attire)”, the Times says.

It correctly predicted the break-up of Demi Moore and Ashton Kutcher, Pamela Anderson and Kid Rock, and Britney Spears and Kevin Federline.

Next on the doomed list, the Times says, are Will Smith and Jada Pinkett Smith. Although they're still married, tabloid reports are filled with rumours of a split ahead of their December 15th anniversary.

Sundem has refined his methods and says that he now studies not so much the amount of fame involved so much as the type of fame, measuring not just Google hits, but mentions in the New York Times versus those in the supermarket tabloid National Enquirer.

“It's tabloid fame that dooms you,” he says.

And it's the wife's fame that matters most: “A high NYT/ENQ ratio also explains why Chelsea Clinton and Kate Middleton have better chances than the Kardashian sisters.” - Sapa-AFP