S.D. Codified Laws § 55-5-11

The circumstances that the trustee may consider in making investment decisions include, without limitation, the general economic conditions, the possible effect of inflation, the expected tax consequences of investment decisions or strategies, the role each investment or course of action plays within the overall portfolio, the expected total return, including both income yield and appreciation of capital, and the duty to incur only reasonable and appropriate costs. The trustee may consider related trusts and the assets of beneficiaries when making investment decisions.