When ministers start demanding evidence before they make decisions, they should be encouraged. So it was right for John Denham, the Skills Secretary, to challenge members of the Association of Colleges about whether their merger mania was really the best thing for their students.
Now we have a response to his claim that there is no evidence that larger colleges provide a better education. An analysis of inspection grades and college size shows that simply being a larger college is likely to get you halfway to the next highest Ofsted rating.
That is a significant gain. And those principals who have lobbied hard for their own mergers to be approved will no doubt feel pleased that their belief in larger institutions has been vindicated, not just because they offer better value for money, but because most of the time they offer a better education.
A defence of larger institutions is also a defence of colleges themselves, whose great strength against schools is the wide curriculum on offer because of their size.
But mergers are not without their problems. They can bring more efficiency, but behind that lies the spectre of redundancies for lecturers and other staff. If several colleges consolidate on one large site, then students can face travel difficulties. On the other hand, colleges that sprawl across disparate sites are bound to be harder to manage.
Moreover, as the study makes clear, the benefits of size are not endless - as the colleges get bigger and bigger, the improvements tend to tail off.
There is another reason for the rush to expansion. Among the scenarios identified in the report where a college was likely to be successful was where it was so large it dominates its local market. One example is Newcastle College, whose empire is beginning to spread across the country.
Colleges are increasingly facing competition from small school sixth forms, despite the fact that they offer students less curriculum choice. Added to that, the programme of building academies is determined to create 11-18 schools in areas where students in the past would have moved on to college.
Competitors tend to seek to establish monopolies. In business, if people over exploit a market and profits are too high, new competitors tend to emerge.
In education, there is no such mechanism and colleges are going to try to grow as large as they can to protect their position - and their students. So if the Government is really concerned that colleges are getting too big, it needs to stop creating conditions where they have every incentive to expand.