The study explores how changes in interest rates affect the number of companies, their size, economic growth, and social welfare in a Schumpeterian economy with an endogenous market structure. Higher interest rates lead to slower growth, smaller firms, and lower levels of output, consumption, and employment. In the long run, interest rate changes do not impact economic growth or firm size, but they do affect the number of firms. Social welfare decreases as interest rates rise, with zero interest rates being the most beneficial for the economy.