Improvement by degree or natural talent?

The problem of signalling is just one of a number of difficulties with the cost benefit analysis of educational expenditure that have been known for decades. Others include the interdependence of the variables explaining earnings (eg IQ), the relationship between earnings and productivity, the use of historic data and the consumption element of HE 'investment.' Many of the same problems will afflict any prospective student attempting to judge the returns to their 'purchase'. This then makes the attempt to establish more effective objective 'market information' problematic.