Federal Funds Rate: MMRFX's yield, and thus price, closely tracks the Federal Reserve's federal funds rate. When the Fed raises rates, MMRFX's yield tends to increase, potentially impacting its price.

Treasury Yields: As a money market fund investing in short-term, high-quality debt, MMRFX is sensitive to fluctuations in Treasury bill yields. Higher Treasury yields can lead to higher yields for the fund.

Credit Risk: Although MMRFX invests in high-quality assets, perceived changes in creditworthiness of issuers (like banks or corporations issuing commercial paper) can affect demand and, consequently, its price.

Supply and Demand: Overall investor demand for money market funds influences MMRFX's price. Increased demand can push prices slightly higher, while reduced demand can lower them.

Fund Expenses: The fund's expense ratio impacts the net yield available to investors. Higher expenses mean lower net yields, which can indirectly affect the fund's attractiveness and price.

Economic Conditions: Broad economic factors like inflation, unemployment, and GDP growth influence interest rate expectations and investor sentiment, indirectly affecting money market fund prices.