Database: olympics
Question: In the 2014 Winter game, what is the percentage of competitors who age 28 years old?
SQL: SELECT CAST(COUNT(CASE WHEN T2.age = 28 THEN 1 END) AS REAL) * 100 / COUNT(T2.person_id) FROM games AS T1 INNER JOIN games_competitor AS T2 ON T1.id = T2.games_id WHERE T1.games_name = '2014 Winter'