In the past I've analyzed my races using this Age Grading Calculator on the web. It was interesting because I could see how I performed compared to a statistical analysis of thousands of other racers. The only problem with the web-based calculator is that it didn't calculate for Marathons or Half Marathons.
Recently someone on one of the Yahoo! racewalking groups I belong to posted an Excel file that calculates age grading for more distances, including the Marathon and Half Marathon. I've been looking at all my races and comparing my performances. Here are some quick statistics:
My performance in my first race (Flagpole 8k on 7/4/03) was 50.57%. My best performance was 7 months later at the Mardi Gras Half Marathon (2/28/04) and was 60.46%.
As I suspected, I'm better at long distances than at middle distances. My best 5k performance is 59.24%. My two best half marathons were 60.01% and 60.46%. My recent marathon was 59.68%, better than I expected.
These spreadsheets work for both runners and walkers, so if you'd like a copy please e-mail me and I'll send it to you.