How many graduate students does each faculty member at a research university supervise to PhD completion? Compare that number to 1 (the number needed to replace that faculty member on retirement) to see how unlikely it is to get a faculty job at a research university.
Probably means that most PhD graduates eventually go elsewhere:
- Faculty at universities other than PhD granting research universities.
- Faculty at community colleges.
- Faculty at high schools.
- Research or other jobs in industry or government (non-academic).
A math major probably has more non-academic options than those of many other majors.