Negative interest rates are a prevalent topic on European financial markets since the early 2010s. Nevertheless the modeling methods in companies and other insti- tutions adjust slowly. This thesis investigates methods for modeling interest rates and presents examples of application fields. As a prime example, Austrian pension funds are considered and how they might have to adjust to a negative interest rate environment. The population structure of Austria is examined and additionally the pension system of Austria is introduced briefly. A life expectancy model is develo- ped specifically for Austrian data and feasibility ratios are calculated according to different methods. The results show that negative interest rates can have a strong impact on the feasibility of pension fund agreements, meaning that an adverse inte- rest rates development will make pension contracts totally unattractive for potential subscribers. As a small complement, yield curves and their behavior in a negative interest environment are considered.