Founded in 1943 in a tiny town in southern Sweden, the IKEA brand is now worth about $11 billion, making it one of the most valuable brands in the world.

This has made 88-year-old founder Ingvar Kamprad very wealthy: Forbes estimates that he's worth $3.8 billion.

If you ask Malcolm Gladwell, whose books have been read by more than 4.5 million people, Kamprad has succeeded thanks to an often-unpopular personality trait: disagreeableness. It's one of the Big 5 personality traits, along with extroversion, emotional stability, conscientiousness, and openness to experience.

On stage at the World Business Forum in New York last week, Gladwell argued that legendary entrepreneurs — like Kamprad and Steve Jobs — have the rare combination of conscientiousness, openness, and disagreeableness.