Write SQL query to solve given problem: Calculate the percentage of people who were born after 1970 and from California.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(SUM(CASE WHEN birth_region = 'California' AND SUBSTR(birthdate, 1, 4) > '1970' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(birthdate) FROM Person;