So, one could say that one of the main problems of the economic analysis in to conceive a scenario for the future evolution of the inflation. To overcome this problem a common and simple economic approach based on a constant market prices system referred to a given year is generally applied in the comparison of costs and benefits either of a project or of alternative design solutions for the same. This approach, which will be adopted in the present chapter, assumes that it is not necessary to account for the inflation, as it will have the same effect in any monetary flux. The future costs and benefits are, then, evaluated at present market prices.