the usual topics ***, salary, seniority!
How true, very market driven and with the current downturn hardly surprising that basic rates seem to have been rather static for years.
However, its also generally true that the higher qualified ( or perceived to be ! ) will attract higher rates by being in demand for specialist skills, eg TRE/IRE, ( those were the days ) other training, or management/consultancy experience.
Generally, the 'big' jump comes moving from Mid to Heavy Iron, there is a smaller gap between Light and Medium, and also the rarity of the species....not many drivers around...up go the rates for the job!
Lastly, don't be fooled into taking domestic USA figures and converting into Sterling/Euro, it just doesn't work!