US Capital Growth over Time
It is important to note that valuation is not a direct measure of productivity as might be indicated by an engineering measure of leveraged human effort, a utilitarian measure of energy conservation. In an efficient market system, valuation is set by the instant cost of all the ingredients required to produce the final product, including the labor embodied in that product. A skill set of any degree of expertise that is in abundant supply in a free market will have the market value of that skill reduced to a fungible level, requiring only the amount required to sustain that human capital in the present, without regard to long term maintenance and care.