Atlas Shrugs quotes Astute Blogger:
Of the thirty (30) nations on the list (being the thirty with the greatest IMBALANCE, with far more men than women - and far more than might be expected if there were no intervention - 20 of them are predominantly Muslim (or with a very large Muslim segment of the population).Or see the red areas on the maps here. While I'm not certain of the reason that so much of the Muslim world has high male/female ratio, it could be infanticide, but I don't think that there's been any studies of that.