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:
Education

Context:
At the level of the individual, there is a large literature, generally related to the work of Jacob Mincer, on how earnings are related to the schooling and other human capital. This work has motivated a large number of studies, but is also controversial. The chief controversies revolve around how to interpret the impact of schooling. Some students who have indicated a high potential for learning, by testing with a high intelligence quotient, may not achieve their full academic potential, due to financial difficulties.[citation needed]

Question:
What was one of the main concerns of this literature on how schooling and earnings?

not achieve their full academic potential, due to financial difficulties