# Debunk IRR: Why is IRR not always the best when measuring the return on your initial investment?

## Understanding the Limitations of IRR

When it comes to evaluating the potential success of an investment, the Internal Rate of Return (IRR) is often touted as a key metric. It represents the discount rate at which the net present value (NPV) of all cash flows (both positive and negative) from a particular investment is zero. While IRR can be a useful measure, it is not without its limitations and may not always be the best indicator of an investment’s return. Let’s delve into why relying solely on IRR might not paint the full picture.

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### The Reinvestment Rate Assumption

One of the main criticisms of IRR is its implicit assumption that all cash flows can be reinvested at the same rate as the IRR itself. This can be highly unrealistic, especially in volatile markets or for investments that yield significantly different returns over time. The assumption fails to take into account the actual reinvestment opportunities available, which could potentially lead to overestimating the profitability of the investment.

### Multiple IRRs and No IRR Situations

Projects with alternating cash flows, where positive cash flows are followed by negative ones (or vice versa), can result in multiple IRRs. This occurs because the IRR equation can have more than one solution. Furthermore, there are cases where an investment does not have an IRR at all, particularly when the net present value never crosses zero. These scenarios can cause confusion and mislead investors who might not be aware of the complexities involved.

### Size and Timing of Cash Flows

The IRR method does not account for the scale of the investment. A smaller project with a higher IRR could be less profitable in absolute terms than a larger project with a lower IRR. Additionally, the IRR does not give weight to the timing of cash flows, which can significantly impact the actual value and risk of an investment. For instance, earlier cash flows are generally preferable as they can be reinvested sooner, yet IRR treats all cash flows equally regardless of when they occur.

The first investment on the left produces cash flow each year, while the second does not. Although both investments produce a 10% IRR, one is clearly more profitable than the other. The reason is that in the first investment, the unrecovered investment balance changes from year to year, while in the second investment it does not.

As a result, the IRR could conflict with other measures of investment performance, such as the equity multiple or net present value. This is one reason why the IRR can be useful as an initial screening tool, but shouldn’t be used in isolation.

Let's look at another example:

- Option 1: Invest 100 at time 0 and get back 200 at time 1. This results in a 100% IRR, and a gross profit of 200-100 or 100.
- Option 2: Invest 1,000,000 at time 0 and get back 1,100,000 at time 1. This results in a 10% IRR, and a gross profit of 1,100,000 – 1,000,000, or 100,000.

Even though option 1 has a higher internal rate of return, option 2 has the highest profit. This can happen because IRR ignores the size of the project.

### Comparing Projects with Different Lifespans

Investments with differing durations can be problematic to compare using IRR. A shorter-term project with a high IRR might seem superior to a longer-term project with a lower IRR. However, the longer-term project could potentially yield more cash over its lifetime. The IRR does not provide clarity in these situations, and additional analysis is needed to make an informed decision.

### Alternative Measures of Return

Given these limitations, investors and analysts often turn to other metrics alongside IRR to gauge investment performance. The Modified Internal Rate of Return (MIRR), for example, addresses the reinvestment rate issue by assuming reinvestment at the project's cost of capital or at a more realistic rate of return. The Net Present Value (NPV) is another crucial metric, providing a dollar amount that represents the value added by the investment, taking into account the time value of money.

### IRR in Context

While IRR can be a valuable tool in the investor's toolkit, it is important to understand its limitations and to use it in conjunction with other financial metrics. By doing so, investors can gain a more comprehensive understanding of the potential returns and risks associated with their investment choices. It is always recommended to perform a thorough analysis that considers various scenarios and assumptions to ensure a robust investment decision-making process.

### Conclusion

In conclusion, IRR is not the be-all and end-all when it comes to measuring the return on investment. Its limitations, such as the reinvestment rate assumption, issues with non-conventional cash flows, and the lack of consideration for the size and timing of cash flows, suggest that it should not be used in isolation. Savvy investors should look beyond IRR and employ a range of financial metrics to paint a clearer picture of an investment’s true potential. By doing so, they can make more informed decisions that align with their financial goals and risk tolerance.