- Era of pre-colonialism – i.e. period before the invasion of the whites.
- Era of colonialism: i.e. period of foreign rule by the whites.
- Era of post-colonialism: i.e. period after the foreign rule by the whites which led to improved life style both in administration, trade and commerce and industrialization.
- Era of post — civil war: This could also be seen as the era of oil boom. It is the period after the civil war of 1967/70.