In games that can be played on Wii, what is the percentage of games released in 2007?
Wii refers to platform_name = 'Wii'; percentage = MULTIPLY(DIVIDE(SUM(release_year = 2007), COUNT(release_year)), 100.0); released in 2007 refers to release_year = 2007;
SELECT CAST(COUNT(CASE WHEN T2.release_year = 2007 THEN T3.game_id ELSE NULL END) AS REAL) * 100 / COUNT(T3.game_id) FROM platform AS T1 INNER JOIN game_platform AS T2 ON T1.id = T2.platform_id INNER JOIN game_publisher AS T3 ON T2.game_publisher_id = T3.id WHERE T1.platform_name = 'Wii'