Members of some social groups - e.g. middle-class, middle-aged, white men - are more likely to become MPs. In contrast, women, black people, young people, working-class people and people with disabilities are under represented among MPs. This under-representation = seen as a problem in a representative democracy - MPs do not represent a cross-section of the population. E.g. women's interests are not represented adequately in the male-dominated House of Commons