Write SQL query to solve given problem: What is the percentage of Japanese cars in the database?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(SUM(CASE WHEN T2.country = 'Japan' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(*) FROM production AS T1 INNER JOIN country AS T2 ON T1.country = T2.origin