Underlying Index Performance: The primary driver is the performance of the index the ETF tracks. If the index goes up, the ETF price generally rises, and vice versa.

Supply and Demand: Market demand for the ETF itself influences its price. Higher demand tends to push prices up, while increased selling pressure can lower them.

Net Asset Value (NAV): The NAV, representing the total value of the ETF's holdings per share, acts as a theoretical fair value. The market price typically stays close to the NAV.

Expense Ratio: The ETF's operating costs, reflected in its expense ratio, indirectly impact returns. Higher expenses can slightly reduce the fund's overall performance and attractiveness.

Investor Sentiment: General market optimism or pessimism can influence ETF prices, even if the underlying index remains relatively stable. Fear or greed can lead to price fluctuations.

Tracking Error: How closely the ETF mirrors its benchmark index affects perceived value. Lower tracking error is usually seen as positive, potentially supporting a higher price.