Among the customers with an average income per inhabitant above 3000, what percentage are in their eighties?
average income per inhabitant above 3000 refers to INCOME_K > 3000; eighties refer to age BETWEEN 80 AND 89; DIVIDE(COUNT(INCOME_K > 3000 and age BETWEEN 80 AND 89), COUNT(INCOME_K > 3000 )) as percentage;
SELECT CAST(SUM(CASE WHEN T1.age BETWEEN 80 AND 89 THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.ID) FROM Customers AS T1 INNER JOIN Demog AS T2 ON T1.GEOID = T2.GEOID WHERE T2.INCOME_K > 3000