And?  Do you understand "compounding" increases?

That 7% figure, which by the way is too low based on the 6 fold increase in Muslim population between 1991 and 2011, if extrapolated out to 2080 translates to 49% by 2080.

Ibbitson's 7% figure represents an approximately 4.5% increase per year between now (where Muslims represent just over 3% of the population) and 2036. 

Do the  math between 2036 and 2080 - over 44 years. It comes out to about 49%. And that, as I say, is low based on increases between 1991 and 2011.

Or maybe the numbers are lying.