What does 'portfolio weights' refer to in the context of portfolio risk?

Portfolio weights refer to the proportion of each asset in the portfolio, which is a critical concept in portfolio risk management. By understanding the weights of each asset, investors can assess how much of their total investment is allocated to different assets and how these allocations contribute to the overall risk and return profile of the portfolio.

When calculating portfolio risk, it is important to consider both the individual risks of the securities involved and their respective weights. The weights essentially determine how much influence each security has on the portfolio's overall risk and return. A higher weight in a volatile asset means that the portfolio may experience greater fluctuations in value, thereby increasing overall risk.

The other options address different aspects of portfolio management. Historical performance provides insight into how assets have behaved in the past but does not dictate how they should be weighted in a portfolio. The level of risk of each security is a separate metric that helps assess individual asset risk but needs to be contextualized with portfolio weights for a comprehensive understanding. Volatility in market returns refers to fluctuations in the market as a whole, which can impact portfolio performance but does not define the weights of assets within a portfolio itself. Therefore, the notion of portfolio weights is fundamentally about asset allocation within a portfolio.