03. Cumulative Returns
PRDTM2-786 AI Trading C3 L1 3 Cumulative Returns V4
Understanding Arithmetic Returns
Concept of Arithmetic Returns
- Measure of investment performance.
- Calculated as (ending value - beginning value) / beginning value.
Limitations
- Not suitable for multi-period analysis.
- Returns do not simply add up over time.
Example
Starting Investment: $10 million.
First Year Result:
- Ending value: $11 million.
- Arithmetic Return: 10%.
Second Year Result:
- Ending value: $9.9 million.
- Arithmetic Return: -10%.
Misinterpretation of Returns
- Adding 10% and -10% yields a return of 0%, which is incorrect.
- Each year's return is based on its preceding year's ending value.
Conclusion
- Correct calculation reflects a negative return of 1% over two years, highlighting the need for proper calculations beyond simple arithmetic addition.
SOLUTION:
- Arithmetic returns are not time-additive, meaning simple addition does not provide an accurate measure of total return over multiple periods.
- The total return over multiple periods should be calculated by multiplying the returns for each period, not by adding them.