In a recent article for Forbes Magazine, Kathy Kristof writes about “The Great College Hoax,” which debunks the premise that student debt will be offset by higher lifetime earnings. Kristof discusses the census finding that, on average, college-educated individuals earn $25,900 more per year than high school graduates, pointing out the fallacy of inferring too much about the reasons for this income discrepancy.

Student Loan Bubble sees a much more serious statistical error in this reasoning: recent graduates earn less at the beginning of their careers, and average (also called “mean”) earnings are a distorted representation of actual earnings. A few individuals (so-called outliers) who earn much more than the rest will distort the mean, while the median will be resistant to this problem. Wikipedia provides the following explanation of median versus mean:

The median is primarily used for skewed distributions, which it represents differently than the arithmetic mean. Consider the multiset { 1, 2, 2, 2, 3, 9 }. The median is 2 in this case, as is the mode, and it might be seen as a better indication of central tendency than the arithmetic mean of 3.166.

Calculation of medians is a popular technique in summary statistics and summarizing statistical data, since it is simple to understand and easy to calculate, while also giving a measure that is more robust in the presence of outlier values than is the mean.

The following table, entitled “Earnings By Occupation and Education,” presents median yearly earnings for individuals aged 21-24, broken down by educational attainment. Click on the image for the full-size version. The original census data are available from http://www.census.gov/hhes/www/income/earnings/call1usboth.html

Students cannot expect to earn an “average” amount of money; in this case, the median is a much more accurate picture of reality. Among recent graduates, the median income discrepancy between college and high school grads is a mere $7,415, which is accompanied by tens of thousands in student debt repayment. Later in life, a college degree is “worth more,” but student debt repayment usually begins when the student is 21 or 22 years old; student lenders are not content to wait until the debtor earns a higher annual income.

It is the conclusion of Student Loan Bubble that the median income statistic deserves more attention, and that lifetime earnings are a misrepresentation of what recent graduates can expect to earn. Between college and high school graduates, loan debt uniquely affects the former, who do not earn dramatically more than the latter. College graduates in their early 20s are at unique risk of not earning enough to repay their student debts. The risk inherent in managing student loans as a young professional may not be offset by future earning potential.

Excerpt from: http://www.forbes.com/forbes/2009/0202/060.html

Census figures show that college grads earn an average of $57,500 a year, which is 82% more than the $31,600 high school alumni make. Multiply the $25,900 difference by the 40 years the average person works and, sure enough, it comes to a tad over $1 million.

But anybody who has gotten a passing grade in statistics knows what’s wrong with this line of argument. A correlation between B.A.s and incomes is not proof of cause and effect. It may reflect nothing more than the fact that the economy rewards smart people and smart people are likely to go to college. To cite the extreme and obvious example: Bill Gates is rich because he knows how to run a business, not because he matriculated at Harvard. Finishing his degree wouldn’t have increased his income.

All the while students have been lulled into thinking of the extra $1 million that will be theirs, they have been forced to disgorge an ever larger fraction of it in pursuit of the degree. While the premium that college grads earn over high schoolers has remained relatively constant over the past five years, the cost of acquiring a degree has risen at twice the rate of inflation, dramatically undermining any value a sheepskin adds.

Offsetting that million-dollar income discrepancy is the $46,700 four-year cost of tuition, fees, books, room and board at a public school and $99,900 at a private one–even after financial aid, scholarships and grants. Add all this to the equation and college grads don’t pull even with high school grads in lifetime income until age 33 on average, the College Board says. Even that doesn’t include the $125,000 in pay students forgo over four years.