Track how often any given card has been practiced overdue

(This is just an idea, not a full "request" per se.)

When exported to an XML file, the current metadata of each card tracks the easiness, number of lapses, and other such data. It might also be interesting to include fields like "Number of times practiced late," "Average number of days late," or other related items.

I was thinking of this feature in terms of controlling experimental data. For example, if a group of subjects is supposed to practice every day but half of the subjects only actually practice once every two days (i.e. being consistently late), then this could have a confounding effect on the results if there were no record of the lateness.