I think the problem is what happens with time. Imagine that you have a graduate in a time when the economy is doing poorly. There will be lots of people out o

I think the problem is what happens with time. Imagine that you have a graduate in a time when the economy is doing poorly. There will be lots of people out of work and competing for jobs, so salaries (in general) should be less generous. Later, if the market picks up, then that year's crop of hires will have higher salaries. Fast forward a few years. Assuming that the difference in skill levels is negligible, salary differences could still be significant. Now, imagine that salaries become public...