We identified three main reasons why the House of Commons should better reflect the social characteristics of our society. The first, and most important, reason is justice: the representative body of our society should have a place within it for all sections of society. The second reason is effectiveness. The House of Commons will work most effectively if it holds within its membership the same diversity of life experiences as are present in wider society. The third reason is to enhance Parliament's legitimacy as an institution. The absence of a wide cross-section of society in the House of Commons can mean that it suffers from a lack of legitimacy. We also noted evidence both from the UK and from other countries which suggests that socially diverse parliaments establish different priorities for Government action. For instance in the UK it has been noted that, after 1997, when the percentage of women in the House of Commons rose from 9% to 18% of