The main currency of politics is killer facts: striking points that move a debate on. In higher education, current killer facts include the claim from the Institute for Fiscal Studies (IFS) that the poorest graduates in England leave university with debts of £57,000 and that interest on student loans has increased to 6.1%.

People often complain that policymakers use figures scrawled on the back of fag packets that are so rough-and-ready they turn out to be incorrect – witness the current debate over whether or not we will recover £350 million a week when we leave the European Union. But that is not the main problem in my view.

Most of the time, politicians do not use figures of questionable provenance. A bigger issue is that some killer facts predominate beyond their true importance and drive out other points that can be just as significant. It is as if we can only focus on a small number of striking points at any one time.

Take those two killer facts, for example. Graduates do indeed emerge with debts of over £50,000 but the IFS themselves also say most graduates do not pay off the entirety of their loan. So it is not at all clear why this one figure should get so much more attention than others. Similarly, it is true that the maximum interest rate on student loans has increased to 6.1% but, after leaving university, the maximum rate only applies to the subset of graduates earning more than £41,000 – and, again, most students are not expected to pay off the entirety of their loan, including the interest applied. (It is also worth noting that the 6.1% interest rate is not a record new high, as some recent coverage has tended to imply – for example, between 2012 and 2014 interest was applied at a higher rate than this.)

Our obsession with debt and interest have crowded out other important facts. There is one in particular that should be up there with – or even above – the others.

Three years ago, Professor Sir David Watson wrote in his last HEPI paper: ‘More than half of our registered students were, and remain, not on full-time first degrees.’ In other words, the typical caricature of a student (a young, full-time undergraduate) was not representative of the majority, for the UK had succeeded in creating what Watson called ‘a remarkably open and responsive HE sector.’ Here is the full extract:

Nationally, we had created, against the official tide, a remarkably open and responsive HE sector. More than half of our registered students were, and remain, not on full-time first degrees. We have led Europe in terms of mature student participation, enrolment of those with registered disabilities – and despite propaganda to the contrary – we are behind only Finland in the participation of students from lower socio- economic backgrounds (Ramsden, 2003). Historically we have led the world in the professional accreditation of higher education qualifications. Forty years ago we invented a particularly powerful and effective Open University (OU). We have an amazingly innovative formal and informal adult education network. Look, for example, at the University of the Third Age (U3A) with nearly 900 centres and nearly 300,000 learners. By 2015 we shall have raised the participation age (and hence the springboard into post-compulsory education) to 18.

The other killer fact we should – but are not – focusing on is that this has changed. According to the headline data from the Higher Education Statistics Agency shown in the chart below, in 2005/06 only 43% of students were full-time undergraduates. In contrast, a decade later the figure was 10% higher at 53%, meaning all other students make up a minority. We now longer have such ‘a remarkably open and responsive HE sector’ and the old caricature of a student has become an accurate representation of the majority in a way that was not always true in the past.

Above all, this reflects the dramatic decline in part-time students in England. And, if we were to strip out mature students from the undergraduate numbers or look at the figures for England only, then the caricature of a student would almost certainly be in a much bigger majority still.

Does any of this matter for policymaking? Yes. It shows why our current obsession with the interest rates, thresholds and fee caps for full-time undergraduate tuition fee loans is far from the only important area for debate. That group of students are already the most robust in terms of demand for higher education.

Post-Brexit, we will need to rely on the skills of our home-grown talent more than in the past. So we need to make sure everyone has the chance to become more educated. The current debate is unlikely to take us much closer to that important goal and may even be doing harm by obscuring some more important points.