A university endowment's Investment Policy Statement (IPS) specifies a perpetual time horizon and a required nominal return of 6.0% annually to cover spending and maintain purchasing power. The IPS also articulates a 'moderate' willingness to take risk. Current capital market expectations suggest that a diversified portfolio typically associated with 'moderate' risk is projected to yield only 4.5% annually. In developing the strategic asset allocation for this endowment, what is the most appropriate approach for the lead portfolio manager to address this apparent inconsistency?