That is why different projections of boundary changes will produce slightly different results, as you will see in the next few days I suspect. (ukpollingreport.co.uk)
The reason why different projections are used is precisely because we have no clue how technology or economic growth are going to change things 100 years down the line. (realclimate.org)
You get three different projections based on whether you retire early, at full retirement age, or at 70. (sapling.com)