I have been mulling over this question for a while. Take Asia, for example - Japan (the most economically developed country) does really badly, with only about 3% of central government positions going to women, whereas Philippines (much less developed) has nearly half of senior posts in government going to women.
I get that cultural norms obviously play a big role here, but cultural norms against women taking part in political life can be found in many Asian societies that have nonetheless managed to produce much higher numbers of female political leaders than Japan.
Clearly economic development alone is not the answer to improving women's rights - just look at China, where women's political rights, political participation and property rights are being rolled back now at a time of prosperity after dramatic improvement under Communism when incomes were generally very low.
And although Islam is not renowned for its focus on women's rights, some Muslim countries have done very well for women in politics - eg Bangladesh certainly scores better on women in positions of power than many other non-Islamic countries. This is hard to fit with what we know culturally of Islam.
I can't work out the answer to why some countries do so much better than others, despite economic development/culture/religion, so I thought I would put it out here to see what everyone else thinks!