Underlying Index Performance: SPXB11.SA's price closely tracks the S&P 500 index's performance. Positive returns in the S&P 500 generally lead to an increase in SPXB11.SA's price, while negative returns usually cause a decrease.

Exchange Rate Fluctuations: As SPXB11.SA replicates a US-based index, exchange rate fluctuations between the Brazilian Real (BRL) and the US Dollar (USD) influence its price. A stronger USD relative to the BRL tends to increase the ETF's price in BRL, and vice versa.

Supply and Demand: Market forces of supply and demand for SPXB11.SA shares also play a role. Increased demand typically pushes the price higher, while increased supply can lower it.

Expense Ratio: SPXB11.SA has an expense ratio, which is deducted from the ETF's returns. A higher expense ratio can slightly reduce the overall return and potentially affect the ETF's price relative to the underlying index.

Replication Strategy: The ETF's replication strategy (e.g., full replication, sampling) can introduce tracking error, meaning SPXB11.SA's performance might not perfectly mirror the S&P 500. This discrepancy can affect its price.

Market Sentiment: Overall investor sentiment towards the US stock market and global economic conditions can influence the demand for SPXB11.SA and consequently its price.