Translate the following question to SQL: In which year were most of ships built?

Schema: CREATE TABLE captain (
    Captain_ID INT   PRIMARY KEY,
    Name TEXT,
    Ship_ID INT,
    age TEXT,
    Class TEXT,
    Rank TEXT,
    UNIQUE (Captain_ID),
    FOREIGN KEY (Ship_ID) REFERENCES Ship(Ship_ID)
);

CREATE TABLE Ship (
    Ship_ID INT   PRIMARY KEY,
    Name TEXT,
    Type TEXT,
    Built_Year REAL,
    Class TEXT,
    Flag TEXT,
    UNIQUE (Ship_ID)
);
user
SELECT built_year FROM ship GROUP BY built_year ORDER BY count(*) DESC LIMIT 1
assistant