The introduction is usually in present tense due to the fact that you are presenting facts and background information on your research topic. By having this information in present tense, you are ...

The present tense describes what's happening now. Depuis is used with the present tense to say how long something has been happening. Learn how to form sentences using the present tense.

Note that apart from if and when ... The implication is that the structure is tricky as it eliminates the present simple. The dominant tense is the past + would + infinitive: If Nigerian ...