A team of researchers led by Michael T French, professor of health economics at the University of Miami (UM), found that a one-point increase in high school GPA raises annual earnings in adulthood by around 12 per cent for men and 14 per cent for women.
"Conventional wisdom is that academic performance in high school is important for college admission, but this is the first study to clearly demonstrate the link between high school GPA and labour market earnings many years later," said French, director of the Health Economics Research Group (HERG) in the Department of Sociology at the UM College of Arts and Sciences, and corresponding author of the study.
For this reason, the researchers analysed men and women separately. Even so, the study found that a one-point increase in GPA doubles the probability of completing college - from 21 per cent to 42 per cent - for both genders.
The results also show that if GPA and other measures of performance are excluded from the analysis model, it gives the impression that African-American men achieve lower educational levels than their white counterparts.
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But, when these predictors are part of the analyses, it demonstrates that African-American men and women attain higher educational levels than white students with the same high school GPA and background characteristics.
"One possible explanation for this finding is that African-Americans with relatively high GPAs are more motivated and determined than whites to attend college and obtain an advanced degree," French added.
The study used multiple waves of data from the National Longitudinal Survey of Adolescent Health. The information included high school records, demographic and background information from more than 10,000 males and females.
The findings were published in the Eastern Economic Journal.