In what year will Britain be 100% learning disabled?

http://www.guardian.co.uk/society/2011/may/31/care-failing-those-with-learning-disability

" ... people with a learning disability, whose numbers are growing by up to 5% a year ... " 

If the number of people with a learning disability are growing by 5% a year, how long will it be before the British are 100% retarded?