Government bond yields: VSZDX primarily invests in short-term U.S. Treasury securities, so its price is highly sensitive to changes in short-term Treasury yields. Higher yields typically lead to lower fund prices, and vice versa.

Interest rate expectations: Expectations about future Federal Reserve interest rate policy heavily influence Treasury yields and, consequently, VSZDX's price. Anticipated rate hikes can depress prices, while expected rate cuts can boost them.

Economic conditions: The overall health of the U.S. economy impacts Treasury yields. Strong economic growth often leads to higher yields, potentially lowering VSZDX's price, while economic weakness can lead to lower yields and higher prices.

Inflation: Inflation erodes the value of fixed-income investments. Rising inflation expectations typically push Treasury yields higher, negatively impacting VSZDX's price.

Credit risk (limited): While VSZDX invests in U.S. Treasuries (considered virtually risk-free), broad market perceptions of U.S. creditworthiness can still have a minor impact. A perceived increase in U.S. credit risk could lead to higher yields and lower prices.

Supply and demand: The overall supply and demand for short-term U.S. Treasury securities also plays a role. Increased demand for these securities pushes prices up (yields down), while increased supply pushes prices down (yields up).