Employment based on individuals in your start class. Despite the statements related to the firm caring about employees, it has proven that this is not the case. PwC hires employees to fire employees. When more work is available they hire based on meeting the need with the intention to fire employees when there is no longer a need.
Although your performance reviews may be solid, if the individuals that you start with have stronger reviews your job will depend on their rank compared to yours.
Introverts beware, if you are not involved with activities within the firm your career will suffer tremendously.