Lesson 10: AnnuitiesThis lesson discusses annuities in the context of the compound interest functions presented in Assessors’ Handbook Section 505 (AH 505), Capitalization Formulas and Tables. The lesson: Show
Definition of an AnnuityAn annuity is a series of equal cash flows, or payments, made at regular intervals (e.g., monthly or annually). The payments must be equal, and the interval between payments must be regular. The following compound interest functions in AH 505 involve annuities:
Ordinary AnnuityAn ordinary annuity is an annuity in which the cash flows, or payments, occur at the end of the period. An ordinary annuity of cash inflows of $100 per year for 5 years can be represented like this: The cash flows occur at the end of years 1 through 5. And the first cash flow occurs at the end of year 1. Most appraisal problems involve ordinary annuities; that is payments are assumed to occur at the end of the period. All of the formulas and factors in AH 505 pertain to ordinary annuities only. Annuity DueAn annuity due is an annuity in which the cash flows, or payments, occur at the beginning of the period. An annuity due is also called an annuity in arrears. An annuity due of cash inflows of $100 per year for 5 years can be represented like this: The cash flows occur at the beginning of years 1 through 5. And the first cash flow occurs at time 0 (now). Practical Applications Converting Annuity FactorsAs noted, most appraisal problems assume that payments occur at the end of the period (ordinary annuity). But if payments occur at the beginning of the period (annuity due), an ordinary annuity factor in AH 505 can be converted to its corresponding annuity due factor with a relatively simple calculation. Although financial calculators and spreadsheet software make it even easier to convert from an ordinary annuity to an annuity due, it is useful to understand how to "manually" convert the ordinary annuity factors in AH 505 to annuity due factors. Conversion of ordinary annuity factor to annuity due factor for FW$1/P or PW$1/P: To determine the Future Worth of $1 Per Period (FW$1/P) or Present Worth of $1 Per Period (PW$1/P) factor for an annuity due, refer to the corresponding factor in AH 505 for an ordinary annuity and multiply it by a factor of (1 + the periodic interest rate). The periodic rate will differ depending on the compounding interval in the problem. For example, with annual compounding, the periodic rate would be the same as the annual rate; with monthly compounding the periodic rate would be the annual rate divided by 12. Example 1: Conversion to annuity due factor for FW$1/P Solution:
Example 2: Conversion to annuity due factor for PW$1/P Solution:
Conversion of ordinary annuity factor to annuity due factor for SFF or PR: To determine the Sinking Fund Factor (SFF) or Periodic Repayment (PR) Factor for an annuity due, refer to the corresponding factor in AH 505 for an ordinary annuity and divide it by a factor of (1+ the periodic interest rate). Be sure to divide, not multiply, when converting the SFF and PR factors. Note: the periodic rate will differ depending on the compounding interval in the problem. Example
3: Conversion to annuity due for SFF Solution: Example 4: Conversion to annuity due for PR Solution: Are annuities where the compounding period is equal to the payment period?All annuity calculations require the compounding period to equal the payment interval. If this is not already the case, then you must convert the expressed interest rate into an equivalent interest rate. For simple annuities, no conversion is necessary since the frequencies are the same: CY=PY.
What do you call the annuities where the payments are made at the beginning of each payment interval?Annuity due is an annuity whose payment is due immediately at the beginning of each period. Annuity due can be contrasted with an ordinary annuity where payments are made at the end of each period. A common example of an annuity due payment is rent paid at the beginning of each month.
Is an annuity where payments are made at the end of each payment interval with the first payment made on a later date?An ordinary annuity is a series of regular payments made at the end of each period, such as monthly or quarterly. In an annuity due, by contrast, payments are made at the beginning of each period. Consistent quarterly stock dividends are one example of an ordinary annuity; monthly rent is an example of an annuity due.
Are annuities compounded monthly?As with all ordinary annuities the payments are made at the end of each payment interval. It is also the case that the compounding interval equals the payment interval. This means that if the payment interval is monthly then interest will also be compounded monthly.
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