You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Nigeria

Context:
Education in Nigeria is overseen by the Ministry of Education. Local authorities take responsibility for implementing policy for state-controlled public education and state schools at a regional level. The education system is divided into Kindergarten, primary education, secondary education and tertiary education. After the 1970s oil boom, tertiary education was improved so that it would reach every subregion of Nigeria. 68% of the Nigerian population is literate, and the rate for men (75.7%) is higher than that for women (60.6%).

Question:
When did Nigeria improve its tertiary education?

After the 1970s oil boom