Eventually these ladders have a top. The 20th century is a mere aberration in growth in human timescales. It's easy to say this is the best - but we're simply biased - it was the best, for us, for a time, largely due to hegemony. The cracks are rapidly showing. Eventually knew value can't be created out of massive scientific advancements (low hanging fruit) we've had. New value will come from others (labor cost reductions to the far east, for example.)