Lane Kenworthy, writing on the subject, includes this graph:
Coincidentally, in a Philosophy Bites episode Anne Phillips argues for equal (or near-equal) representation by gender, among other criteria.
Participatory democracy is impractical, so most democracies are representative democracies. But should the representatives reflect the variety of those they represent? In particular, should there be roughly half women in a representative democracy? Anne Phillips of the LSE believes that there should be far more women acting as political representatives than there are at present. In this interview for Philosophy Bites she explains why.
Largely missing from Phillips’s discussion is the question of whether we should be looking at opportunity or outcome (recognizing a close link between the two). Regardless, the poor representation of women in the US and UK legislatures is surely an indication that something needs fixing.