Researchers have tried and failed to fully understand why so many people are unwilling to plunge into the stock market and ride the ups and downs of an investment that pays off over the long haul. A new study finally lands on something that has the power to affect how people invest: personality. In fact, personality is as good at explaining investment decisions as the sex, age, income, wealth, and education of individuals combined, said researchers at Northwestern, DePaul University, and the London School of Economics. They examined the Big 5 personality traits: openness, conscientiousness, extraversion, agreeableness, and neuroticism. Openness and neuroticism have the most influence on stock investing – with opposite effects. On the other hand, agreeableness, characterized by…