Don't know the answer to your question but came across this remarkable statistic from an interview with Dr Hans-Joachim Schopf (formerly director of Sindelfingen plant)
"Of the 440,00 cars produced in that plant in 1998, only three were totally identical"
If anyone has an account with JD Power they may be able to access the data.
In my last job I had access to it and I recall that at their peak roughly 250k were being made per year. But this tends to rapidly drop away each year thereafter.