I finally understand the difference in my calculation of the SOTP average closing price and the official one. The difference comes from two angles:
First, the history price used in the official calculation is NASDAQ Official Closing Price (NOCP), which is difference than the last trading price what Yahoo! Finance and MSN Money usually use. This summary explains details of NOCP.
Second, according to Microsoft, November 28 (the day after Thanksgiving) is not a full trading day and thus is not included in the calculation. (I didn't find it is mentioned in all the documents though).
Below is how the official average closing price gets calculated:
Date |
Official Closing Price |
Avg Official Closing Price |
14-Nov-03 |
$ 25.46 |
$ 25.4600 |
17-Nov-03 |
$ 25.21 |
$ 25.3350 |
18-Nov-03 |
$ 25.15 |
$ 25.2733 |
19-Nov-03 |
$ 25.35 |
$ 25.2925 |
20-Nov-03 |
$ 25.09 |
$ 25.2520 |
21-Nov-03 |
$ 25.11 |
$ 25.2283 |
24-Nov-03 |
$ 25.75 |
$ 25.3029 |
25-Nov-03 |
$ 25.41 |
$ 25.3163 |
26-Nov-03 |
$ 25.49 |
$ 24.3356 |
1-Dec-03 |
$ 25.85 |
$ 25.3870 |
2-Dec-03 |
$ 25.68 |
$ 25.4136 |
3-Dec-03 |
$ 25.62 |
$ 25.4308 |
4-Dec-03 |
$ 26.20 |
$ 25.4900 |
5-Dec-03 |
$ 25.96 |
$ 25.5236 |
8-Dec-03 |
$ 26.25 |
$ 25.5720
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