Since yesterday night, I been trying to redo my excel file to calculate XIRR. Thanks to guidance from Cory, LP and CW in cbox I managed to complete the XIRR for both my accounts with the start date of 13th May 2011.  (I do not have detailed data before this.) It can be easily seen that the XIRR values vary a lot with or without considering investible cash as part of the equation. Basically there are two schools of thoughts

1. Equity
2. Equity + investible cash

For method 1, we should only consider pure equity return to measure the performance and cash should not be included as cash is subjective. For method 2, we should only consider investible cash as part of the equation as one constantly input funds from one earned income into investible fund. This measure if one has effectively made full use of the investible cash ......