Making a large salary certainly isn't the only motivation for attending college. If it happens to be one of the reasons you signed on for four years at a institution of higher learning, however, you'll find Georgetown University's new study on the Economic Value of College Majors to be an illuminating read. Compiled by professors from the university's McCourt School of Public Policy's Center of Education and the Workforce, the study breaks down which majors pull in the highest salaries in the U.S., both at the entry-level mark and beyond. The average starting salary for a worker with a Bachelor's degree is $33,000 per year, growing to $61,000 at "prime age." But, the study found, there's a large disparity between the highest paying majors and the lowest — almost $3.4 million over a career. It won't come as a huge surprise that a STEM degree (science, technology, engineering, and math) proved to be the most lucrative, with entry-level employees earning $43,000. By contrast, workers with a degree in the arts, liberal arts, or humanities brings home a $29,000 annual salary to start. The pay disparity continues throughout one's career, with a STEM major earning $30,000 more per year on average than someone who majored in teaching or service. The wage gap increases as STEM majors are more likely to pursue graduate degrees, thus boosting their salary premium. Not all STEM majors are created equal when it comes to money, however: Petroleum engineering was ranked as the most lucrative major overall, with an average annual wage of $136,000 for workers age 25 to 59. Pharmacy, pharmaceutical sciences, and administration ranked second at $113,000, while computer science came in 11th at $81,000. Of the 25 highest-earning majors, only economics and business economics (placing 24th and 25th, respectively) represented non-STEM majors. What of the 25 lowest-earning majors? They overwhelmingly fall under teaching, with early child-education majors coming in last with an average salary of $39,000 a year. A few exceptions are the fields of neuroscience ($48,000) and anthropology and archaeology ($49,000). Despite the low wages of certain industries, you're still better off graduating from college, whatever you study. A degree of any kind will command a higher salary than merely a high school diploma, which earns entry-level workers just $22,000 a year on average.