How many percent of orders in 2020 used international shipping?
international shipping refers to method_name = 'International'; orders in 2020 refers to order_date = '2020%'; percentage = Divide (Sum(method_name = 'International'), Count(order_id)) * 100
SELECT CAST(SUM(CASE WHEN T2.method_name = 'International' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(*) FROM cust_order AS T1 INNER JOIN shipping_method AS T2 ON T1.shipping_method_id = T2.method_id WHERE STRFTIME('%Y', T1.order_date) = '2020'