Janet Jackson's career as a hitmaker has been a model of consistency, rivaling Madonna and Whitney Houston in terms of pop-chart success over the long haul. A big part of the reason was that Jackson kept her level of quality control very high; her singles are always expertly crafted, with indelible pop hooks and state-of-the-art production that kept up with contemporary trends in urban R&B. Once established, her broad-based appeal has never really dipped all that much. She successfully shifted her image from a strong, independent young woman to a sexy, mature adult. With a string of multi-platinum albums under her belt, she shows signs of slowing down in the new millennium. In 2008, Jackson released Discipline. She continues to tour the world.