30% is the relevant point at which it is said that “a large minority can make a difference, even if it is still a minority”.
As per Rosabeth M. Kanter (1), critical mass is the theory that women and racial or ethnic minorities are unlikely to have an impact in the boardroom until they grow from a few tokens into a considerable minority of the board.
1) Rosabeth Moss Kanter holds the Ernest L. Arbuckle Professorship at Harvard Business School, specializing in strategy, innovation, and leadership for change