Less than half of Americans -- 47% -- are satisfied with their jobs, according to a 2006 survey of 5,000 households released Friday by the Conference Board. The dissatisfaction is growing. Last year marked the first time a majority of respondents have said they're unhappy at work, according to the occasional survey from the private research organization. Twenty years ago, about 61% of workers were happy with their jobs. In 2005, 52% were satisfied. ...The happiest workers are those over 55, those who make more than $50,000 a year, those who put in more than 50 hours a week on...