Reuven Brenner claims that shortening college would have major economic benefits:

There are at least 16 million youngsters enrolled in post-secondary education, with approximately 4 million graduating every year. Assume that from now on, each year, 4 million students join the labor force a year earlier. Each generation would stay one year longer in the labor force. How much annual income and how much wealth would this generate?

Assume that after graduation the average salary would be just \$20,000 and remain there. With 4 million students finishing one year earlier, this would add \$80 billion to the national income during that year. Or at an average annual income of \$40,000, it would add \$160 billion. Assume now that the additional \$80 billion in national income would be compounding at 7 percent over the next 40 years. This would then amount to an additional \$1.2 trillion of wealth – for just one generation of 4 million students joining the labor force a year earlier at a \$20,000 salary. At \$40,000, this would amount to \$2.4 trillion by the fortieth year – again, for just one generation of 4 million people joining the labor force a year earlier. The added wealth depends on how rosy one makes the assumptions about salaries or compounding rates. Add 10, 20, or 30 generations, each starting to work a year earlier, and the numbers run into the tens of trillions of dollars.