The portfolio motive also focuses on demand for money over and above that required for carrying out transactions. The basic framework is due to James Tobin, who considered a situation where agents can hold their wealth in a form of a low risk/low return asset (here, money) or high risk/high return asset (bonds or equity). Agents will choose a mix of these two types of assets (their portfolio) based on the risk-expected return trade-off. For a given expected rate of return, more risk averse individuals will choose a greater share for money in their portfolio. Similarly, given a person's degree of risk aversion, a higher expected return (nominal interest rate plus expected capital gains on bonds) will cause agents to shift away from safe money and into risky assets. Like in the other motivations above, this creates a negative relationship between the nominal interest rate and the demand for money. However, what matters additionally in the Tobin model is the subjective rate of risk aversion, as well as the objective degree of risk of other assets, as, say, measured by the standard deviation of capital gains and losses resulting from holding bonds and/or equity.