Deaths among former slaves has proven hard to estimate, due to the lack of reliable census data, though they were known to be considerable, as former slaves were set free or escaped in massive numbers in areas where the Union army did not have sufficient shelter, doctors, or food for them. Professor Jim Downs states that tens of thousands to hundreds of thousands of slaves died during the war from disease, starvation, or exposure, and that if these deaths are counted in the war's total, the death toll would exceed 1million.