0
$\begingroup$

Given total index return for a single period can be characterized as :

$$TR_{1}=\sum_{i=0}^Nw_i \frac {(p_{1i}-p_{0i}+inc_i)}{p_{0i}} $$

Is there a way to rewrite or derive a multi-period form of the above where inputs are returns (in percentage form) of the price and income components of the total return?

Ex:

If a security market index has a price return of 10% and an income return of 2% for period 1, and a price return of 15% and an income return of 3% for period 2, what is the approach to finding total return based only off of these kind of percentage inputs?

$\endgroup$
0

1 Answer 1

1
$\begingroup$

Assuming $N$ is the number of securities in the index and $w_i$ is the weight of security $i$, one can rewrite $TR_{1,0}$, the total return of the index from time $0$ through $1$, as

$$ \begin{align*} TR_{1,0} &= \sum_{i=1}^Nw_i \frac {(p_{1,i}-p_{0,i}+c_{1,i})}{p_{0,i}} &&<\text{definition}> \\ &= \sum_{i=1}^Nw_i (p_{1,i}/p_{0,i}-p_{0,i}/p_{0,i}+c_{1,i}/p_{0,i}) &&<\text{algebra}> \\ &= \sum_{i=1}^Nw_i (p_{1,i}/p_{0,i}-1+c_{1,i}/p_{0,i}) &&<\text{algebra}> \\ &= \sum_{i=1}^Nw_i (pr_{1,i}+cr_{1,i}) &&<\text{substitute }pr_{1,i}=p_{1,i}/p_{0,i}-1, cr_{1,i}=c_{1,i}/p_{0,i}> \tag 1 \end{align*} $$

where $p_{j,i}$ is the price of security $i$ at time $j$, $c_{j,i}$ is the income of security $i$ from time $j-1$ through time $j$, $pr_{j,i}$ is the price return of security $i$ from time $j-1$ through $j$, $cr_{j,i}$ is the income return of security $i$ from time $j-1$ through $j$.

Equation (1) can be generalized as

$$ TR_{j,j-1} = \sum_{i=1}^Nw_i (pr_{j,i}+cr_{j,i}) \tag 2 $$

where $TR_{j,j-1}$ is the total return of the index from time $j-1$ through time $j$.

The total return of the index from time 0 through time $K$ (the multi-period return) can be calculated by compounding single period returns. This can be expressed as

$$ \begin{align*} TR_{K,0} &= \left( \prod\limits_{j=1}^{K} (TR_{j,j-1}+1) \right) - 1 &&<\text{definition}> \\ &= \left( \prod\limits_{j=1}^{K} \left( \left( \sum_{i=1}^N w_i (pr_{j,i}+cr_{j,i}) \right) +1 \right) \right) - 1. &&<\text{substitute equation (2)}> \tag 3 \end{align*} $$

It is possible to generalize equations (2) and (3) further by assuming weights can change dynamically. Dynamic weights can be expressed as $w_{j-1,i}$ which would be the weight of security $i$ at time $j-1$. Then equation (3) can be rewritten as

$$ TR_{K,0} = \left( \prod\limits_{j=1}^{K} \left( \left( \sum_{i=1}^N w_{j-1,i} (pr_{j,i}+cr_{j,i}) \right) +1 \right) \right) - 1. \tag 4 $$

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.