Which country produced the highest number of cars? Calculate the annual average number of cars that the said country produced from the very start to the present.
the highest number of cars refers to max(country); annual average number = divide(count(ID), count(model_year))
SELECT T2.country, CAST(COUNT(T1.ID) AS REAL) / COUNT(DISTINCT T1.model_year) FROM production AS T1 INNER JOIN country AS T2 ON T1.country = T2.origin GROUP BY T2.country ORDER BY COUNT(T2.country) DESC LIMIT 1