Compound Interest: The Power of Exponential Growth
By Imperialpedia Staff
Compound interest is the addition of interest to the principal sum of a loan or deposit, where interest earned also earns interest. This creates exponential growth and is fundamental to long-term wealth building.
The Rule of 72
The Rule of 72 is a quick way to estimate how long it takes for an investment to double. Simply divide 72 by the annual interest rate to get the approximate number of years for doubling.
Simple vs. Compound Interest
Simple interest is calculated only on the original principal, so it grows in a straight line — a $10,000 deposit at 5% simple interest earns exactly $500 every year. Compound interest is calculated on the principal plus all interest already earned, so the base it's calculated on grows every period, producing a curve that accelerates over time rather than a straight line.
Compounding Frequency
The same annual interest rate can produce slightly different results depending on how often it compounds — annually, quarterly, monthly, or daily. More frequent compounding means interest starts earning its own interest sooner, producing marginally faster growth at the same headline rate. This is why the "effective annual rate" (which accounts for compounding frequency) can be a more accurate comparison tool than the stated annual rate alone.
IMPORTANT
Compounding works in both directions — the same mechanism that grows savings also grows unpaid debt, which is why carrying a balance on a high-interest credit card can become expensive so quickly.
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