Using The Rule To Estimate Compounding Periods
To estimate the number of periods required to double an original investment, divide the most convenient "rule-quantity" by the expected growth rate, expressed as a percentage.
- For instance, if you were to invest $100 with compounding interest at a rate of 9% per annum, the rule of 72 gives 72/9 = 8 years required for the investment to be worth $200; an exact calculation gives 8.0432 years.
Similarly, to determine the time it takes for the value of money to halve at a given rate, divide the rule quantity by that rate.
- To determine the time for money's buying power to halve, financiers simply divide the rule-quantity by the inflation rate. Thus at 3.5% inflation using the rule of 70, it should take approximately 70/3.5 = 20 years for the value of a unit of currency to halve.
- To estimate the impact of additional fees on financial policies (e.g., mutual fund fees and expenses, loading and expense charges on variable universal life insurance investment portfolios), divide 72 by the fee. For example, if the Universal Life policy charges a 3% fee over and above the cost of the underlying investment fund, then the total account value will be cut to 1/2 in 72 / 3 = 24 years, and then to just 1/4 the value in 48 years, compared to holding exactly the same investment outside the policy.
Read more about this topic: Rule Of 72
Famous quotes containing the words rule, estimate and/or periods:
“It seems to be a rule of wisdom never to rely on your memory alone, scarcely even in acts of pure memory, but to bring the past for judgment into the thousand-eyed present, and live ever in a new day.”
—Ralph Waldo Emerson (1803–1882)
“Value dwells not in particular will;
It holds his estimate and dignity
As well wherein ‘tis precious of itself
As in the prizer.”
—William Shakespeare (1564–1616)
“It has no future but itself—
Its infinite contain
Its past—enlightened to perceive
New periods of pain.”
—Emily Dickinson (1830–1886)