Skip to content

Decomposing an uneven stream into an annuity and an extra payment

Payments of 200, 200, 700 and 200 at times 1 to 4 can be decomposed into a four-payment 200 annuity plus 500 at time 3.

On this page

Preserve the original dates

Matching the two representations
TimeOriginal paymentBase paymentExtra payment
12002000
22002000
3700200500
42002000

Value the two components

At 10% per period, base-annuity PV is 633.9731 and the extra payment’s PV is 375.6574. Their sum is 1,009.6305.

Compare with individual discounting

Discounting 200, 200, 700 and 200 separately gives the same sum. A decomposition is useful only if its amounts and dates reproduce the original cash-flow pattern.

Keep the extra payment on its actual date

Moving the extra 500 to time 4 would create a different stream. Cash-flow additivity permits rearranging the representation, not changing the economic timing.

Further references