Database: regional_sales
Question: Between 2018 to 2020, what is the average amount of shipped orders per year under Carl Nguyen?
SQL: SELECT CAST(COUNT(T1.OrderNumber) AS REAL) / 3 FROM `Sales Orders` AS T1 INNER JOIN `Sales Team` AS T2 ON T2.SalesTeamID = T1._SalesTeamID WHERE (T2.`Sales Team` = 'Carl Nguyen' AND ShipDate LIKE '%/%/18') OR (T2.`Sales Team` = 'Carl Nguyen' AND ShipDate LIKE '%/%/19') OR (T2.`Sales Team` = 'Carl Nguyen' AND ShipDate LIKE '%/%/20')