Central banks use overnight interest rates to control monetary policy, affecting the entire yield curve. High volatility in the federal funds market can disrupt this relationship. Research shows that studying actual federal funds rates instead of expected rates can lead to rejection of the expectations hypothesis in money markets. Lower volatility in bank funding markets can result in lower long-term rates. These findings apply to the US, Euro Area, and UK. The closer short- and long-term rates are linked, the more likely the expectations hypothesis holds.