A website called The Washington Center for Equitable Growth has an article that expresses uncertainty over the declining relationships (a) between earning a college degree and income and (b) between choosing the right in-demand college major and income. COTTonLINE wonders at the economic naivety this uncertainty shows.
Perhaps the very first law of economics is the reciprocal effects of supply and demand on price. More demand pushes prices up, more supply pushes prices down. In this case "price" is income, what the market is willing to pay for a person's labor.
As demand weakens, as seen in increased rates of underemployment/unemployment, and supply of college grads increases as ever greater numbers attend and graduate (a) from college and (b) from higher demand majors, we would expect what? We would expect prices to fall: in this case a decline in the wage premium that a baccalaureate degree once demanded.
Not only is this not rocket science, it is the most elementary economics - truly Econ 1A, basic microeconomics. I taught the class decades ago before specializing in Management.