While stock selection often gets the most attention, the true driver of portfolio performance is typically asset allocation, with around 90% of variability linked to how investments are distributed across asset classes. Different asset classes perform well under different economic conditions—stocks might excel in growth periods, while bonds provide stability during downturns. 

Goldman Sachs has analyzed various economic scenarios to suggest optimal asset mixes for maximizing risk-adjusted returns over the next decade. For sluggish growth or stagflation, they recommend a heavier allocation to Treasury bonds and real assets, while minimizing exposure to growth stocks. 

In a scenario of strong growth and low inflation, the maximum allocation to stocks should still be capped around 70%. Ultimately, a diversified mix, including US Treasuries, remains crucial regardless of the economic outlook.

Finsum: Keep in mind the relative risk profiles of these asset classes when constructing your portfolio.