How do large scale, involuntary migrations and population exchanges affect sending and receiving communities? We examine the case of the partition of India in which approximately 17 million people moved within four years, resulting in one of the largest and most rapid population exchanges in human history. We find large effects due to the migration on a district's educational, occupational, and gender composition. Due to higher education levels amongst migrants, districts with 10 per cent greater inflows saw their literacy rates increase by 3 percentage points, while a 10 per cent increase in outflows reduced literacy by 1.2 percentage points. Due to disparities in the amount of land vacated by migrants, Indian districts with 10 per cent greater inflows saw a decline of 11 per centin agricultural occupations. Districts that experienced high inflows and outflows also experienced changes in gender composition. While the partition, driven along religious lines, increased religious homogenization within communities, our results suggest that this was accompanied by increased educational and occupational differences within religious groups. We conclude that these compositional effects, in addition to an aggregate population impact, are probably features of involuntary migrations and population exchanges and, as in the case of India, Pakistan, and Bangladesh, can have important long-term consequences.