This is a question of economic growth, which this paper handily explains... http://www.stanford.edu/~promer/EconomicGrowth.pdf http://www.stanford.edu/~promer/

This is a question of economic growth, which this paper handily explains... http://www.stanford.edu/~promer/EconomicGrowth.pdf http://www.stanford.edu/~promer/EconomicGrowth.pdf If you believe it's feasible for economic growth to continue, then you believe it's feasible for the indexes to continue to rise, perhaps to something that rounds to infinity (at least for my purposes).