For investors looking to build wealth over the long term, the strategy of consistent, monthly contributions to an S&P 500 index fund is frequently highlighted as a reliable method. By investing $100 every month for 20 years, an individual benefits from the historical average annual return of the S&P 500, which is often cited as approximately 10% before accounting for inflation.

Over two decades, this consistent habit results in a total principal investment of $24,000. Due to the power of compounding—where earnings generate their own earnings—the final balance can grow significantly higher than the total amount contributed. While exact results vary based on market performance, the core principle remains that time in the market is often more effective than attempting to time the market.

Financial experts generally agree that this "dollar-cost averaging" approach reduces the risk of investing a large lump sum at a market peak. However, it is important to note that past performance is not a guarantee of future results. Market volatility can cause short-term fluctuations, and investors must be prepared for periods where the portfolio value may decrease. Furthermore, the impact of management fees and inflation can erode the purchasing power of the final sum, a factor that is sometimes overlooked in simplified growth projections.