To better understand the impact of a portfolio manager’s choices in asset allocation on the portfolio's overall additional return, it is necessary to evaluate how different allocations between asset classes can influence performance. Asset allocation involves distributing investments among various categories like stocks, bonds, and cash, each with its own risk and return characteristics. By strategically choosing the proportion of each asset class, the portfolio manager aims to optimize the portfolio's return for a given level of risk.

Given this context, what is the effect of a portfolio manager's asset allocation decisions on the portfolio's total additional return?