Interest Rate Environment: Changes in the Federal Reserve's interest rate policy directly impact the yield, and therefore the price, of FMJXX.

Market Liquidity: High demand for safe, liquid assets can drive up the fund's price; conversely, reduced demand can lower it.

Economic Conditions: Overall economic health and investor sentiment influence the flow of funds into or out of money market funds like FMJXX.

Credit Risk Perception: Perceived creditworthiness of the fund's underlying holdings (Treasuries, repurchase agreements) affects its appeal and price.

Fund Management Strategy: The investment decisions of the fund's manager, including portfolio composition and maturity structure, influence performance and price.

Supply and Demand: The basic economic principle of supply and demand affects the price. High demand and limited supply will raise the price, while low demand and high supply will lower it.