List and explain five difficulties in collecting population data in west africa

There are a multitude of difficulties that exist in West Africa that make finding population data difficult. 

Conflict- historically and currently there are countries in West Africa that have had widespread conflict. 
Disease- outbreaks of diseases like Ebola in West Africa have hampered the ability to conduct research. 
Weak States- weak governments in West African countries make it difficult to obtain accurate census data. 
Two other factors could also be the lack of proper infrastructure making travel difficult and also the region is divided into many different countries making conducting research in a multitude of environments at once more difficult.