Under the efficient-frontier framework, the assumption that investors are risk-averse, i.e., they prefer returns and distaste risks. In other words, investors prefer higher returns and lower risks. If two different portfolios have two different returns, but the same level of risk, then the higher return portfolio dominates the lower return portfolio (it is preferred to it). Likewise, if return is the same for the two portfolios, an investor will select the less risky portfolio. The dominance principle is usually used to illustrate the risk-return trade-off. It allows an investor to hold one variable (risk or return) constant, while he makes decisions based on the value of the other variable.