Diversification with a 401(k) refers to the investment strategy of spreading contributions across various asset classes, such as stocks, bonds, and cash equivalents, to minimize risk. This strategy is grounded in the belief that different asset classes perform differently under varying market conditions. By diversifying, participants in a 401(k) plan can potentially reduce the impact of poor performance in any single investment.

In a 401(k) plan, diversification is achieved through the selection of a mix of investment funds. These funds often include a variety of domestic and international stocks, bonds, and short-term reserves. Some 401(k) plans also offer target-date funds that automatically adjust the mix of assets as the participant nears retirement, becoming more conservative (less risky) over time.

The idea is that by diversifying, the overall investment is less vulnerable to the volatility of any single market or asset class. If one asset class experiences a downturn, the others may not be as affected, which can help to stabilize or even improve the overall performance of the 401(k) portfolio. This approach is a fundamental principle for risk management in investing and is particularly important in retirement planning, where the goal is often to build and maintain wealth over the long term with a manageable level of risk.