That's not a direct comparison, though - that's all people with a high school diploma versus all people with a college degree. To draw any conclusion off this,

That's not a direct comparison, though - that's all people with a high school diploma versus all people with a college degree. To draw any conclusion off this, you'd need to compare people who were considering college but do not attend versus those who were considering college but did attend - even if they didn't graduate. Only then do you have a metric that you can use to represent the ROI of attending college.