Investment returns redux

I discovered an error with the spreadsheet I used to generate my investment returns. It turns out I hadn't adjusted the S&P 500 index price for some of my purchases. The effect was to make the Benchmark column wrong:

Stock             Opened  Price  Closed   Price Annualized Benchmark
Oracle           6/24/02   8    5/28/03   13.35     67.05%    -9.94%
Major Automotive 2/28/06   1.75 3/29/06    1.90    144.21%   -11.13% 
Oracle           6/24/02   8     4/4/06   13.84     14.99%     6.80%
Canon            12/9/03  45     4/4/06   68.56     19.04%     2.19%
Canon            12/1/04  49.66  4/4/06   68.56     26.38%     5.34%
Select Comfort    2/9/05  19.95  4/4/06   39.80     80.44%     6.60%
Berkshire (B)    1/31/06   2920  4/4/06    3001      8.29%     2.57%

Now I'm 100% both on absolute and relative terms. Obviously this was a pleasant surprize. Even better, I've been tracking my time-weighted internal rate of return and my IRA is earning about 20% annualized. Since I've held a lot of cash earning less than 4% most of that time, I feel pretty confident in my ability to make good investments over time. If anything, I ought to be making more trades.