Final answer:
A decrease in residual income can increase a company's return on investment.
Step-by-step explanation:
To increase a company's return on investment, a decrease in operating income, total assets, and asset turnover ratio would not be favorable. However, a decrease in residual income can increase a company's return on investment. Residual income is the amount of profit a company generates above its required rate of return. By decreasing the residual income, the company can potentially improve its return on investment.