Jan 7, 2020

Cory Diary: Short Coming of Cumulative XIRR of Lifetime Result

Has been in market for more than 15 years. Over the years strategy changed with ones experience and learning. Sometime change for the better, sometimes worst. One indication is using Cumulative XIRR across all trades through the years.

For Cory, due to strong performance in 2019, the Cumulative XIRR since 2007 is now 7.2% as above. However this is from 2007 when Cory is still young man with all sort of ideas. 

How good is it to measure progress over time. Logically the cumulative will have to go up. But is this assumption right ? Let's try another table by injecting additional 10k profit into 2 scenarios. First scenario in Year 2007 and the second scenario in Year 2019 below.

From the above table,  there are much larger improvement in the score in 2007 ( 7.54% ) which is much more than Year 2019 ( 7.36% ) can provides. This is probably due to portfolio size and compounding over the years. What this mean is that it will be harder to push up the cumulative value even with good performance in later year. It will have take few more good years to see recovery.

To overcome this issue, we may have to use rolling years to accommodate this limitation. Here's the table. So you can see at 13th, 10th and 7th Years period  ... is down trend.

Now, if we have a major strategy change 7 years ago, we could see the progress at 5 years, 3 years and 1 year ago. This way "very past" performance do not cloud the future view.

What I am still deliberating is.... if a Guru has fantastic performance in his early years of investment life, will his performance stick with him for later years using cumulative metrics ?


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