I saved the age graded factors that were used when I turned forty so I can get apples to apples;) Latest tables knock me down half a percent .
Details on how the current tables are being updated:
https://runnersconnect.net/age-grading/
Here’s the deal:
If you relied on the current world record, the age grading system would require frequent updates and revisions, and you wouldn’t be guaranteed a smooth progression when moving up in ages.
For example, if the all-time best 5k for a male 58-year-old was 16:00, but the all-time best for a male 59-year-old was 15:58, the same performance would be worse for an older runner, which doesn’t make sense.
Now:
To get around these sorts of problems, age-grading calculators use a smoothed curve to predict the best performance for a given age level. This curve is derived using statistical analysis of top performances, and is extremely close to the actual all-time bests for every age from about 16 to 50, but actual all-time bests jump around outside of that age range.
How reliable is age grading?
Age-grading as a concept is great, but there are a few drawbacks to the current methods used.
First, there are several different “versions” compiled by different statisticians floating around, and these will produce slightly different results when you plug in the same performance level.
Further, as records are broken, the models will eventually need to be updated. Though a smooth curve prediction of age-group bests will last longer without revisions, as more and more records get broken, the formula will gradually get less accurate.
The Howard Grubb / Alan Jones age grading calculator, which is probably the most commonly-used variant, gets updated about every five to ten years.2