There is little response of nominal interest rates to inflationary movements in the second half of the Nineteenth Century, while the Fisher equation would predict a one-to-one relation between these economic variables. Most of the previous answers to this observation rely on some sort of irrationality argument (Fisher (1906), Friedman and Schwartz (1982), Summers (1983) and Barsky and De Long (1991) are some examples) or state that there are problems in the data used (Perez and Siegler (2003)). In this thesis, I argue that this is not due to agent irrationality, but to the lowering of the equilibrium interest rate level as a response to a demographic transition attributed to advances in medical science and enhancements in sanitation infrastructure. I build an stylized overlapping generations model based on Gertler (1999) that captures the main features of the American Economy during this period, then calibrate it and conduct experiments to show that Barsky and De Long s (1991) strike on the Fisher Effect does not hold when the demographic channel is turned off.