Your correspondents who express disquiet at 25 per cent of academic staff being 55 or over, or a third being over 50, are arithmetically challenged ("Stark warning of staff crisis", THES, February 25).
If a typical academic career starts at 25 and ends at 65 then steady-state staffing would indicate precisely 25 per cent being 55 or over, and three-eighths or 37.5 per cent being over 50. The fact that typical academic careers start at a later age means that, if anything, one would expect even higher proportions of staff in the upper age ranges.
So long as it is expected that everyone pulls their weight, and everyone does, a department with due proportions of members over 50 and over 55 has a healthy age structure. With an orderly succession of retirements to come, a regular infusion of new staff is in prospect as replacements, and for those in post the opportunity to move into senior positions and take new responsibilities are not far distant.
Departments where hardly anyone is over 50 have often reached that state through having arm-twisted their over 50s into early retirement in the past. Their future is either for more of that to take place or stagnation.
It is a different and very real concern whether there will be suitable recruits out there, preferably young ones, to fill future vacancies. Let us worry about real problems such as that, rather than imaginary ones.
Charles Goldie School of mathematical sciences University of Sussex