The U.S. Department of Education’s National Center for Education Statistics (NCES) reported that 52% of students who enter college intending to major in mathematics switch to another major. That needs to be balanced with the fact that many more students switch into a mathematics major. In fact, over the past couple decades, the number of students graduating with a major in mathematics has run 50–60% higher than the number who enter intending to major in mathematics.
Data for intended majors are from the HERI Freshman Survey. Number of actual majors is taken from the NCES Digest of Education Statistics. 2015 is the latest year for which they have published degree data. As an example, in 2011, 13,800 students entered intending to major in mathematics, 21,800 graduated in 2015 with a bachelor’s degree in mathematics.
Among the STEM fields of Mathematical Sciences, Bio-Sciences, Computer Science, Engineering, and Physical Sciences, only Computer Science and the Mathematical Sciences see an increase in graduates over intended majors.
The implication is that there is a lot of churn among potential math majors, suggesting that most students entering college do not have a clear idea of what it means to major in the mathematical sciences.