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Perpetuities and Annuities - Corporate Finance - Ivo Welch

Perpetuities and Annuities - Corporate Finance - Ivo Welch

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Growing <strong>Perpetuities</strong><br />

A growing perpetuity pays CF , then CF · (1 + g), then CF · (1 + g) 2 , then ... For<br />

example, if CF = $100 <strong>and</strong> g = 0.10 = 10%, then you will receive the following<br />

payments:<br />

CF0 = 0 = $0 (no discount)<br />

CF1 = $100 = $100.00 (then discount with r0,1)<br />

CF2 = $100 · (1 + 10%) = $110.00 (then discount with r0,2)<br />

CF3 = $100 · (1 + 10%) 2 = $121.00 (then discount with r0,3)<br />

CF4 = $100 · (1 + 10%) 3 = $133.10 (then discount with r0,4)<br />

CF5 = $100 · (1 + 10%) 4 = $146.41 (then discount with r0,5)<br />

<strong>and</strong> so on, forever<br />

The PV of a growing perpetuity can be quickly computed as<br />

∞ CF1 · (1 + g)<br />

PV = ∑<br />

t=1<br />

t–1<br />

(1 + r) t = CF1<br />

(r – g)<br />

You must memorize the RHS formula, <strong>and</strong> know what it means!<br />

◮ The growth term acts like a reduction in the interest rate.<br />

◮ The time subscript for the payment matters now, because C1 = C2.<br />

13/1

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