The authors of this study examine the relationships between historical exposure to Islamic kingdoms and current economic, medical, and educational development in Africa. They predict that ethnic groups that were previously ruled by Islamic states or chiefdoms will have worse outcomes today, theorizing that these worse outcomes would be not as a result of an inherent characteristic of Islam or Islamic kingdoms themselves but rather decreased investment by colonial states or missions. Their results lend some support to their hypotheses, and particularly to the predictions that Christian missions and colonial states would not be able to penetrate areas under Islamic influence as easily as other regions.