Calculate the average crime rate per month in the highest populous area.
the highest populous refers to max(population); average crime rate per month = divide(count(report_no where population = max(population)), 12)
SELECT CAST(COUNT(T2.report_no) AS REAL) / 12 FROM Community_Area AS T1 INNER JOIN Crime AS T2 ON T2.community_area_no = T1.community_area_no GROUP BY T1.community_area_no HAVING COUNT(T1.population) ORDER BY COUNT(T1.population) LIMIT 1