Theory Z is an extension of Theory X and Y that was created by William Ouchi based on a mixture of Japanese and American management practices. It has 10 key characteristics including collective decision making, long-term employment, job rotation, slow promotion, training, care for employees' personal lives, informal but formalized control, individual responsibility, generalist employees, and a strong company culture. These characteristics are meant to create a flexible, permanent, skilled and loyal workforce through consensus, security, flexibility, evaluation, and aligning the employees' goals with the company's goals. However, some argue that Theory Z declined in importance as Japan's economy struggled in the 1990s.