Federal Funds Rate: TBSXX's yield, and thus its price, is closely tied to the Federal Funds Rate set by the Federal Reserve. When the Fed raises rates, TBSXX's yield typically increases, and vice versa.

Treasury Bill Yields: As a money market fund investing in short-term U.S. Treasury securities, TBSXX's performance is directly impacted by the yields of these bills. Higher Treasury bill yields generally translate to higher returns for TBSXX.

Market Interest Rates: Broader market interest rates, including commercial paper rates and certificate of deposit rates, influence TBSXX's competitiveness. A general increase in interest rates across the market can push TBSXX to offer higher yields to remain attractive to investors.

Supply and Demand: Increased demand for TBSXX can drive up its price slightly, while higher supply can lower it. Demand is often influenced by investors seeking a safe haven during times of economic uncertainty.

Fund Expenses: The expense ratio of TBSXX impacts the net yield investors receive. Higher expenses mean a lower net return, indirectly affecting its price relative to other similar funds.

Economic Conditions: Overall economic health, including inflation and GDP growth, can influence the Federal Reserve's monetary policy decisions and, consequently, impact interest rates and TBSXX's performance.