The data for literacy is no more or less solid than the other data. It's just for other data more people agree. NO good reason for that, they just do. All the data is created from nothing. Another often cited factor of the level of misery in Haiti are the death rates of children.
Infant mortality is the highest in the hemisphere.
The death rate of children is astronomical. This seems wrong to me. Children mainly die of malnutrition related diseases. The rap against Haitians is surely false. Nonetheless, there is an enormous problem with AIDS in Haiti, and it is related more to heterosexual transmission than any other form, or so the literature seems to suggest.