Expected Classifications (xC) are the overall position a driver should have finished had all drivers finished consistently and without incident.
For drivers who had to retire or had one or two tricky incidents, xCs are a forgiving measure. They intend to be a measure of a driver’s ability from their performance. If you were to run a given rally again xCs would be a good guide of who to pick in your team.
xCs can also highlight who gained positions due to others falling out. It may look good that a driver finished 2nd, but they wouldn’t be likely to do the same again next time. This is on the basis that another driver who retired or lost time wouldn’t have the same luck again.
xCs are based on a measure used in football analysis of expected goals, or xG. These measures are hypothetical results of matches based on the likelihood of a goal being scored. See this post on median classifications for an example and the origin of xC.
The xC Calculation
UPDATE 23/05/2019: Going forward expected classifications will be calculated from median average pace drop across the stages for each rally. This is calculated as (drivers time – fastest stage time)/length of stage in KM.
Before now, Expected Classifications were quite simply the median average of all completed stage classifications. They do not include Rally 2 times and for this reason a minimum number of stages should be included. For the average 18-20 stage WRC rally PP will use a minimum of 3 stages.