Labor economists generally agree that each extra year of school raises someone's earning by 10-15%. But it turns out that math classes could account for half of those gains.
And we can thank Ronald Reagan for this piece of knowledge. Following a critical report of the American education system by the Reagan administration in 1983, many states around the country raised the number of math and science courses that were required for graduation. In a new paper, Harvard's Joshua Goodman looks at what happened to earnings following the reforms. The higher math requirements (typically from 0 or 1 required courses to 2 or 3 courses) had the biggest impact on schools in low-income, black areas (most likely because white/higher income students were already taking 2 or 3 math classes.)
Goodman finds that:
[B]lacks benefited substantially from the additional math courses they were induced to take by these reforms. Each class is estimated on average to raise blacks' earnings by around 8%. Given that 15% is usually an upper estimate for the value of a year of schooling, these results imply that math coursework can [account for] a substantial portion of that value, at least for blacks.
Overall, however, the increased requirements that followed the Reagan report didn't have a sizable impact on earnings for the nation as a whole -- again, probably because the average student was already taking more than the new minimum requirements.