Find the percentage of products that were shipped from Burbank in 2018?
DIVIDE(SUM(Order Quantity where City Name = 'Burbank' and SUBSTR(OrderDate, -2) = '18')), (SUM(Order Quantity where SUBSTR(OrderDate, -2) = '18')) as percentage;
SELECT CAST(SUM(CASE WHEN T3.`City Name` = 'Burbank' THEN T2.`Order Quantity` ELSE 0 END) AS REAL) * 100 / SUM(T2.`Order Quantity`) FROM Products AS T1 INNER JOIN `Sales Orders` AS T2 ON T2._ProductID = T1.ProductID INNER JOIN `Store Locations` AS T3 ON T3.StoreID = T2._StoreID WHERE T2.OrderDate LIKE '%/%/18'