Inflation Expectations: CPIEX.US, an inflation-protected securities fund, sees its price rise when investors anticipate higher future inflation. This is because its underlying bonds are designed to compensate for inflation, making them more attractive.

Real Interest Rates: Rising real interest rates (nominal rates minus inflation) can decrease CPIEX.US's price. Higher real yields on alternative investments make inflation-protected securities less appealing.

Treasury Yields: Changes in broader Treasury yields also impact CPIEX.US. If Treasury yields increase, even inflation-protected ones might become relatively less attractive, leading to a price decline.

Market Sentiment: General investor risk appetite influences CPIEX.US. During times of uncertainty, investors might flock to safer assets like Treasury Inflation-Protected Securities (TIPS), driving up CPIEX.US's price. Conversely, optimism can lead to decreased demand.

Supply and Demand: Like any fund, CPIEX.US's price is affected by supply and demand. Increased demand relative to supply pushes the price up, and vice versa. This demand is influenced by the factors above.