The acute shortage I am told, is in IT Techs. In short people who fix / install computers / networks or have anything to do with computers including software. ( or should that be soft wear!)
Compare the salary and career prospects of a civilian equivelent, even civil Servants and it does not take biblical brains to work out that this is a lose-lose scenarion. Not least due to the people prepared to bite the bullet are going to be the same who would not 'make-it' in the civil sector.
Look at the other trade requirements, and all have transferable skills that are better paid outside of the military fence. Pay back time methinks from degrading the quality of life and job security that was once the mantra by which the armed forces existed.