And conversely, how do you know which performance measures are the least helpful predictors? Which ones are most susceptible to noise, randomness, and luck?
By running a linear regression of all the major performance stats, focusing on NASCAR's "modern era" (since 1972), and only including drivers who started at least 25 races in consecutive years, we can calculate the slope parameter for each statistic, and can order them by their predictive power.
In this chart, we see all the major performance stats, ranked by their stability across consecutive seasons. Most stable at the top, least stable at the bottom. The most consistent stats from year to year are Average Start and Lead Lap Finishes, while the least consistent stats are Wins and Poles.
Here are some interesting conclusions we can infer from the chart:
3) Crashes, failures and bad luck are a major factor in randomness. Notice that Laps Completed and Races Running at the Finish are near the bottom of the list. Both of these are related to the concept of keeping your car clean and getting it to the finish line in one piece. Think about crashes, engine failures, flat tires, and getting pulled into in accidents caused by others. Drivers can have a good year where everything goes their way, and a bad year where they seem to hit everything around them. Of course these stats are going to be hard to forecast, because effectively you are trying to predict how many accidents a driver will have, and this is very hard to do, when most of these events are out of their control.
Alright, so how can I use this table?
- If you are in a fantasy league, think about which past stats are actually going to be the most useful for you to forecast future performance. Wins and poles don't really help you that much.
- If you are in the media and discussing driver performance, perhaps Lead Lap Finishes is a stat to consider as something that can be repeated over time.
- If you are an owner or sponsor looking to hire a new driver, remember to be careful when considering that driver's past performance statistics. Think about those stats where the driver is doing well: Are they repeatable over time (higher on the table), or perhaps just the result of some good luck (lower on the table)?