I walked through Parliament Square early yesterday afternoon, just before MPs began to debate the coalition government’s controversial proposal to raise student tuition fees. There was at that time little sign of student protestors. The scene instead was one of curious tourists watching the massed ranks of heavily armed police, some on horseback, as though this were an authoritarian alternative to the changing of the guard up the road at Buckingham Palace. No matter how deplorable the subsequent violent behaviour of a minority of demonstrators, there is something menacing about the forces of the state preparing for battle outside the principal institution of our democracy. Let’s hope this isn’t the taste of things to come.

I surveyed the depressing scene en route to participating in a timely lunchtime debate at the Royal Society for the encouragement of Arts, Manufactures and Commerce (RSA), entitled: Is 50 per cent too much? Access to higher education in an age of austerity. While preparing my contribution, it struck me that one of the ironies of the tuition fees debate is that opponents fear the coalition government’s preferred approach will restrict access to higher education, but proponents argue that the policy will, at the very least, maintain the existing quantity and quality of higher education at lower cost to the public purse. Yet whichever side of the debate is right - discussion of the merit of the government’s position, a graduate tax, or sticking with the status quo – all of it is predicated on the assumption that high or rising participation in higher education is an appropriate policy objective.

The assumption reflects the conventional ‘common room’ wisdom, shared by policy makers, academics and students alike, that we need a large supply of graduates in order to promote both economic and social progress. The alternative popular ‘saloon bar’ wisdom (that there are nowadays more university students and graduates than the country either needs or, in tough times, can afford) is dismissed with hardly a second thought. But should it? I must admit that my personal inclination is to support the common room over the saloon bar on this matter. But in doing so I think it’s helpful to put conventional wisdom to the test.

Take, for example, the argument that demand for graduate skills will tend to outstrip supply in a growing knowledge-based economy, and thus that failure to match growth in investment in graduate skills will see UK living standards fall relative to countries that are expanding higher education. As a general rule this argument is quite strong but there is also evidence to support the counter argument that some of the increase in demand for UK graduates in recent decades merely reflects a re-labelling of previously non-graduate jobs as graduate jobs by employers in response to increased student numbers. As a result, a proportion of graduates are found to be ‘overqualified’ for the jobs they are doing, which calls into question the return to investment in graduate skills, whatever the precise funding mechanism.

A related argument in favour of expanding higher education is that graduates earn more over their lifetime than people with A-levels or equivalent qualifications who could have entered higher education but took an alternative route into the workforce. Once again, while this argument holds at face value, the average post-tax lifetime graduate premium of around £100,000 might not adequately measure the return to all graduate qualifications. For some prospective students, the potential relative financial return to graduate and non-graduate employment might be minimal, while it is also possible that non-graduate routes to work - such as work-based apprenticeships - might provide superior soft employability skills of the kind many employers suggest are lacking in graduates.

Question marks over the case for mass higher education doesn’t necessarily provide sufficient justification to put the brakes on expansion but they do strengthen the need for good quality advice and guidance to prospective students, a matter on which everybody seems to be in general agreement and a seriously under-acknowledged positive aspect of the coalition government’s approach. This seems to me the best way to both ensure that entry to higher education is a considered rather than simply automatic choice, and that the distribution of students across higher education institutions and courses is based on a clear assessment of the financial and non-financial rewards on offer. What level of participation such a rational choice-based system will result in is difficult to determine in the abstract – it could be more or fewer students and graduates than we have today. But it is likely to produce an optimal outcome.