Does mathematical education imply a better salary? In some sense this is a follow-up to

Correlation between salary level and housing prices in a town

There I was reminded to ask for causality, not correlation. I am interested in the causal effect of mathematical education on salaries even if I do not use those words below.

Now, my question is the following: does mathematical education result in a better salary? Here, by mathematical education, I do not mean mathematics as a major but rather a major with heavy mathematics in it. Probably a better formulation is this: is there any literature on whether studying applied mathematics pays off? Again not an Applied Mathematics as a curriculum per se, but a course with heavy applied math content.
Math is easier if you are smarter. As such, math education is a costly and therefore credible signal of general intelligence. Below are two experiments that try to get around this selection issue by looking at exogenous variation in worker mathematical ability on labor market outcomes. However, a word of caution. They do not present evidence that mathematical education makes you more productive. Even if all mathematical education is is a signal of intelligence, it can be valuable to individual workers to get more mathematical education, and they will on average benefit from interventions that lower the cost of getting a mathematical education  


  We examine the link between math skills and labor-market outcomes
  using a resume-based field experiment. Specifically, we send
  fictitious resumes in response to online job postings, randomly
  assigning some resumes to indicate stronger math skills, and measure
  employer responses. The resumes that are randomly assigned to indicate
  stronger math skills receive more interest from employers than the
  comparison resumes. Our findings add to the body of evidence showing
  that stronger math skills positively affect labor-market outcomes.


Math skills and labor-market outcomes: Evidence from a resume-based field experiment by Koedel and Tyhurst (2012)


  Outsourcing  of  jobs  to  low-wage  countries  has  increased  the 
  focus  on  the  accumulation  of skills – such as Math skills – in
  high-wage count ries. In this paper, we exploit a high school pilot 
  scheme  to  identify  the  causal  effect  of  advanced  high  school 
  Math  on  labor  market outcomes.  The  pilot  scheme  reduced  the 
  costs  of  choosing  advanced  Math  because  it  allowed for at more
  flexible combination of Math with other courses. We find clear
  evidence of  a  causal  relationship  between  Math  and  earnings 
  for  the  students  who  are  induced  to  choose  Math  after  being 
  exposed  to  the  pilot  scheme.  The  effect  partly  stems  from 
  the  fact  that these students end up with higher education.


Is there a causal effect of high school math on labor market outcomes? by 
Joensen and Nielsen (2009)