Not sure how systematic the research is, but Business Week claims to has the answer from a list drawn up for them by a New York-based human resources company ORC Worldwide (remember this was written for expats):
No. 1 Lagos, Nigeria
Overall Grade: Very High Risk Location
Severe Problems: Infrastructure, Crime
Major Problems: Pollution, Disease & Sanitation, Medical Facilities, Availability of Goods and Services
Other Problems: Climate, Education Facilities, Physical Remoteness, Political Violence & Repression, Political & Social Environment, Culture & Recreation
There’s no more challenging place on ORC’s list than the largest city in Africa’s largest country. Lagos not only has a severe crime problem and extremely poor infrastructure, the city has inadequate housing, sanitation, and medical facilities. Moreover, according to ORC, “the risk of being caught up in sectarian violence is another concern.”
Oh, Baghdad, Pyongyang and Harare–places where there are wars or where the people face economic sanctions–did not qualify. Neither did European, US or Canadian cities.