We all know that there are non-economic influences upon stocks that can be either long-lasting or of short-term duration. One of the real challenges in building a portfolio or selecting a stock is to try to decide how much of a particular influence is already reflected in the price. The ISN models indicate what the present price of the stock should be if the past relationships between the economic influences and the company are unchanged. Stocks, like rubber bands, stretch to overvalued levels that cannot be justified and then snap back, sometimes quickly, sometimes slowly, to a realistic valuation. Also like rubber bands in contraction, the stocks typically overshoot the correct valuation and become undervalued given the economic developments.