PlanetMath (more info)
 Math for the people, by the people.
Encyclopedia | Requests | Forums | Docs | Wiki | Random | RSS  
Login
create new user
name:
pass:
forget your password?
Main Menu
Owner confidence rating: Very high Entry average rating: No information on entry rating
rate of return (Definition)

Suppose you invest $ P$ at time 0 and receive payments $ P_1,\ldots, P_n$ at times $ t_1,\ldots,t_n$ corresponding to interest rates (evaluated from 0) $ r_1,\ldots, r_n$. The net present value of this investment is

$\displaystyle NPV=-P+\frac{P_1}{1+r_1}+\frac{P_2}{1+r_2}+\cdots+\frac{P_n}{1+r_n}.$

The rate of return $ r$ of this investment is a compound interest rate, compounded at every unit time period, such that the net present value of the investment is 0. In other words, if $ r$, as a real number, exists, it satisfies the following equation:

$\displaystyle P=\frac{P_1}{(1+r)^{t_1}}+\frac{P_2}{(1+r)^{t_2}}+\cdots+\frac{P_n}{(1+r)^{t_n}}.$

Remarks.

  • We typically assume that $ t_1\le t_2\le \cdots \le t_n$, and, in most situations, that they are integers, so that the equation is a polynomial equation.
  • However, there is no guarantee that $ r$ exists, and if it exists, that it is unique.
  • Nevertheless, one can usually, by trial-and-error, determine if such an $ r$ exists. If $ r$ exists, and if $ P_i$ are all non-negative, then by Descartes' rule of signs, $ r$ is always unique and $ r>-1$.



"rate of return" is owned by CWoo. [ full author list (2) ]
(view preamble)

View style:

Log in to rate this entry.
(view current ratings)

Cross-references: polynomial, integers, equation, real number, period, unit, compound interest, net present value, interest rates
There is 1 reference to this entry.

This is version 2 of rate of return, born on 2007-02-11, modified 2007-02-11.
Object id is 8896, canonical name is RateOfReturn.
Accessed 572 times total.

Classification:
AMS MSC91B28 (Game theory, economics, social and behavioral sciences :: Mathematical economics :: Finance, portfolios, investment)

Pending Errata and Addenda
None.
Discussion
Style: Expand: Order:
forum policy

No messages.

Interact
post | correct | update request | add derivation | add example | add (any)