Which of the following is a factor that can affect interest rates?

Inflation is a critical factor that affects interest rates because it influences the purchasing power of money over time. When inflation rises, the value of money decreases, prompting lenders to demand higher interest rates as compensation for the erosion of money's value. This adjustment helps maintain the real return on loans and investments. Central banks, like the Federal Reserve in the United States, often raise interest rates to combat high inflation, thereby influencing overall borrowing costs in the economy.

While geopolitical stability, demographic trends, and market sentiment can definitely impact interest rates indirectly, they do not have the same direct relationship with interest rates that inflation does. For instance, geopolitical stability can create a favorable environment for investment, which might lower rates, but it doesn't inherently change the underlying dynamics of currency value like inflation does. Similarly, demographic trends might affect long-term economic growth forecasts, influencing rates over a more extended period, but again, inflation remains a more immediate and direct driver of interest rate fluctuations. Market sentiment can affect investor behavior temporarily but lacks the fundamental impact of inflation on the economy's overall pricing mechanisms.