US stock market performance: VTBIX mirrors the total US stock market. Broad market gains lift VTBIX, declines lower it.

Economic data: Strong economic indicators like GDP growth or low unemployment often boost stock prices, increasing VTBIX's value. Weak data can have the opposite effect.

Interest rate changes: Rising interest rates can make bonds more attractive than stocks, potentially leading to stock market declines and lower VTBIX prices. Lower rates can stimulate stock growth.

Inflation: High inflation can erode corporate profits and dampen investor sentiment, potentially decreasing VTBIX's value. Moderate inflation is often seen as a sign of a healthy economy.

Investor sentiment: Positive investor sentiment towards US stocks drives demand and increases VTBIX prices. Negative sentiment can lead to sell-offs and lower prices.

Company earnings: Strong earnings reports from major US companies typically boost overall market confidence and VTBIX value. Poor earnings can weigh on the fund.

Geopolitical events: Global events like wars or political instability can create market uncertainty and volatility, impacting VTBIX prices. Generally, stability is favored.

Fund flows: Large inflows into VTBIX drive up demand and prices, while outflows create selling pressure and lower prices.

Currency fluctuations: A weaker US dollar can make US stocks more attractive to foreign investors, potentially increasing demand for VTBIX and vice versa.