Question: Calculate the percentage of women who have participated in Equestrianism Mixed Three-Day Event, Individual.
SQL: SELECT CAST(COUNT(CASE WHEN T1.gender = 'F' THEN 1 ELSE NULL END) AS REAL) * 100 / COUNT(T1.id) FROM person AS T1 INNER JOIN games_competitor AS T2 ON T1.id = T2.person_id INNER JOIN competitor_event AS T3 ON T2.id = T3.competitor_id INNER JOIN event AS T4 ON T3.event_id = T4.id WHERE T4.event_name = 'Equestrianism Mixed Three-Day Event, Individual'