$500/month grows to $252,288 in 15 years

A SIP is a disciplined investment method where you invest a fixed amount every month into a mutual fund, ETF, or other investment vehicle. Instead of trying to time the market with a lump sum, SIPs use dollar-cost averaging — buying more units when prices are low and fewer when prices are high, smoothing out volatility over time. Over 15–20 years at 10–12% annual returns, even $300/month becomes a significant sum due to compounding. SIPs are particularly popular in India for mutual fund investing, but the same principle applies to any regular investment globally.

Historical long-run returns from diversified equity index funds have averaged 7–10% p.a. after inflation in developed markets. In Australia, the ASX 200 has returned around 10% p.a. total return (including dividends) over the past 30 years. At 10% p.a., $500/month over 20 years grows to approximately $382,000 — of which only $120,000 is your own contributions. The remaining $262,000 is compound growth. Returns are not guaranteed and vary year to year, but the long-run trend strongly favours consistent monthly investing over staying in cash.

Both have merits. A lump sum invests all your capital immediately, giving it maximum time in the market. Research consistently shows that lump sum investing beats dollar-cost averaging approximately 2/3 of the time in rising markets. However, SIPs offer behavioural advantages: they remove the temptation to time the market, make investing automatic, and work well when you're building wealth from income rather than deploying existing capital. In volatile markets, the psychological benefit of not watching a large lump sum drop 30% is significant. Most financial advisors recommend SIPs for regular income investors and lump sum for those with existing capital to deploy.