How Compound Interest Builds Perpetual Wealth
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The Mechanics
Simple interest pays a return only on the original principal each period. Compound interest pays a return on the principal plus all previously accumulated interest, which is why the growth curve steepens over time rather than staying a straight line.
Why Time Beats Timing
Because each compounding period builds on the last, the number of periods matters enormously — money given more time to compound, even at a modest rate, often outperforms a larger sum given less time, which is the core argument for starting residual income investing as early as feasible.
Applying This to a Residual Income Stack
Compound growth applies most directly to reinvested capital streams (dividend reinvestment, interest-bearing accounts), but the same underlying principle — small early advantages compounding into large later differences — is why the earliest years of building any residual income portfolio matter disproportionately more than they might feel like at the time. Try the free Residual Income Stack Simulator to model your own streams and get your Perpetual Income Score.
Frequently Asked Questions
What is the formula for compound interest?
A = P(1 + r/n)^(nt), where P is principal, r is annual interest rate, n is the number of compounding periods per year, and t is time in years.
Why does starting early matter more than the amount invested?
Because compounding is exponential rather than linear, money invested early has more compounding periods to benefit from, meaning a smaller amount invested early can eventually outgrow a larger amount invested later, all else equal.
Is the 'Rule of 72' accurate?
It's a close approximation for moderate interest rates (roughly 6–10%) — dividing 72 by the annual rate estimates years to double — but becomes less precise at very high or very low rates.