For environmental, social and economic reasons Cornwall (and the UK for that matter) should aim for a steady state population.
How might this be accomplished?
Currently the number of people moving into Cornwall exceeds the number moving out, hence the increase in population. The difference for the period up to 2030 is 4,800 per year.
To attain a steady state population requires a reduction in the number of people moving in of 4,800 or a reduction of 2,400 moving in and an increase of 2,400 moving out.
And how might those targets be attained?
Not building extra houses
Creating jobs that can be filled by residents rather than encouraging in-migration
Not advertising Cornwall as the location to work and play!