&gt;The data is clearly sourced it the wikipedia article. Your data is either old or just wrong.<p>Point me to the line in that article that says that.<p>Here is a quote from the 2nd paragraph.<p>&quot;The overall median personal income for all individuals over the age of 18 was $24,062[6] ($32,140 for those age 25 or above) in the year 2005.[7] The overall median income for all 155 million persons over the age of 15 who worked with earnings in 2005 was $28,567.[8]&quot;<p>Where are you getting 56k from?<p>&gt;Where is the evidence the increase in earnings is the result of the degree rather than selection bias? Correlation is not causation.<p>That is entirely possible, but many studies have attempted to correct for this. Here is a good summary of several.<p><a href="http:&#x2F;&#x2F;www.nytimes.com&#x2F;2014&#x2F;05&#x2F;28&#x2F;upshot&#x2F;the-value-of-college-its-not-just-correlation.html" rel="nofollow">http:&#x2F;&#x2F;www.nytimes.com&#x2F;2014&#x2F;05&#x2F;28&#x2F;upshot&#x2F;the-value-of-colleg...</a><p>There are also a few other problems with your formula. $30k is way too high for an 18 year old just out of high school. And again, 20k per year is closer to the average total yearly cost of a public school.<p>Let&#x27;s say 20k per year in income which is much closer to the median starting salary for an 18 year old. Let&#x27;s also say that if it costs a college student 10k a year to live that it only costs a non-college student 5k to account for extra costs for the college student.<p>So we have 20k a year in lost income and 15k a year in costs over what the student would have paid had they not attended.<p>That&#x27;s 4x20k + 4x15k = 140k. About half of your estimate.<p>That also doesn&#x27;t take into account that college students are free during breaks to work, or take paid internships. 
College only takes about 30 weeks per year, while the workers will be working about 50 weeks out of the year. (Also Engineering and Computer Science internships in particular pay fairly well.)