There appears to be a wide-spread consensus that countries want economic growth. It is, however, unsual for coutries to set themselves explicit long-term growth targets. We have therefore used the average of the observed and estimated GDP growth rates for the period of 2002-2013 to extrapolate future GDP until 2030.
This is similar to a company that uses future hurdle rate for the use of capital based on past performance of the benchmark. There is no guarantee that the benchmark will reach this efficiency in the future. The extrapolation based on past performanc can however serve as an estimate for future performance.