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'
database name:db_id books
address_status table address_status Cols: status id dtype integer, address status dtype text, 
author table author Cols: author id dtype integer, author name dtype text, 
book_language table book_language Cols: language id dtype integer, language code dtype text, language name dtype text, 
country table country Cols: country id dtype integer, country name dtype text, 
address table address Cols: address id dtype integer, street number dtype text, street name dtype text, city dtype text, country id dtype integer, 
customer table customer Cols: customer id dtype integer, first name dtype text, last name dtype text, email dtype text, 
customer_address table customer_address Cols: customer id dtype integer, address id dtype integer, status id dtype integer, 
order_status table order_status Cols: status id dtype integer, status value dtype text, 
publisher table publisher Cols: publisher id dtype integer, publisher name dtype text, 
book table book Cols: book id dtype integer, title dtype text, isbn13 dtype text, language id dtype integer, number pages dtype integer, publication date dtype date, publisher_id dtype integer, 
book_author table book_author Cols: book id dtype integer, author id dtype integer, 
shipping_method table shipping_method Cols: method id dtype integer, method name dtype text, cost dtype real, 
cust_order table cust_order Cols: order id dtype integer, order date dtype datetime, customer id dtype integer, shipping method id dtype integer, destination address id dtype integer, 
order_history table order_history Cols: history id dtype integer, order_id dtype integer, status id dtype integer, status date dtype datetime, 
order_line table order_line Cols: line id dtype integer, order id dtype integer, book id dtype integer, price dtype real, 
