I suppose it would not convince him to present statistics that correlate income with literacy in the world, and especially with literacy in English. It would be seen as crass to suggest that income means success. In the middle ages, monks would take a vow of poverty so they could seek knowledge by reading. Language and literacy allow you to communicate with others, and to expand your access to information and ideas. Literacy was seen as more important than wealth.
Poverty goes with illiteracy.
This applies to any language. People who can communicate only with a limited circle of neighbors are handicapped. On a typical day, I can read and join into conversations going on between people in Finland, Singapore, India, England, Israel, Australia, Japan, Nigeria, or practically anywhere else. Because they all communicate in English.