Interest Rate Changes: TSPXX's yield, and thus its attractiveness, directly reflects short-term interest rate movements. A rise in rates generally leads to a higher yield for TSPXX.US, making it more appealing to investors.

Treasury Bill Yields: As TSPXX invests in Treasury bills, their yields serve as a benchmark. When Treasury bill yields increase, TSPXX's yield tends to follow, influencing its price.

Economic Conditions: Overall economic health and expectations of future growth or recession can indirectly impact TSPXX's price by affecting interest rate policy and investor sentiment towards riskier assets.

Federal Reserve Policy: The Federal Reserve's monetary policy decisions, especially those related to short-term interest rates and the money supply, significantly affect TSPXX's yield and, consequently, its price.

Investor Demand: High demand for safe, liquid assets, often during times of uncertainty or market volatility, can drive investment into TSPXX, potentially influencing its price and yield slightly.

Inflation Expectations: Rising inflation expectations may lead to higher interest rates, which can subsequently increase the yield of TSPXX and make it more attractive relative to other investments.