It's a frightening statistic. But before you rush out and hire a detective or challenge your partner head-on, you should first be sure whether your suspicions are reasonable or just the imaginings of very jealous mind.
What you shouldn't do is let your suspicions take over your life, nor ignore them and hope they'll go away.
Helene, a British expatriate living in Hong Kong, did the latter, choosing to ignore suspicions about her husband Jon.
"Of course, the signs seem obvious looking back," she says. "Business calls on the mobile at all hours, regular business trips overseas even over weekends, a sudden interest in hair products ..."