Underlying Stock Performance: SDP tracks the S&P 500 Equal Weight index. Therefore, the collective performance of the 500 stocks in that index directly impacts SDP's price.

Market Sentiment: Overall investor optimism or pessimism regarding the U.S. stock market significantly affects demand for SDP. Positive sentiment can drive prices up; negative sentiment can push them down.

Interest Rates: Changes in interest rates influence the attractiveness of stocks relative to bonds. Rising rates may decrease demand for stocks, thus affecting SDP, and vice versa.

Economic Data: Key economic indicators such as GDP growth, inflation, and unemployment influence investor confidence and corporate earnings, which in turn affects stock prices and SDP.

Sector Performance: While SDP is equally weighted, the relative performance of different sectors within the S&P 500 can still influence its price depending on sector composition.

Supply and Demand: Basic market forces dictate that high demand for SDP, relative to its supply, will drive its price up, while increased supply and decreased demand will lower its price.