system: You are a text-to-SQL generator. Given a database schema and a question, reply with a single valid SQLite query that answers it. Output only the SQL on one line, with no explanation and no markdown.

user: Schema:
CREATE TABLE film_text (
  film_id integer PRIMARY KEY,
  title text,
  description text
);
CREATE TABLE actor (
  actor_id integer PRIMARY KEY,
  first_name text,
  last_name text,
  last_update datetime
);
CREATE TABLE address (
  address_id integer PRIMARY KEY,
  address text,
  address2 text,
  district text,
  city_id integer,
  postal_code text,
  phone text,
  last_update datetime
);
CREATE TABLE category (
  category_id integer PRIMARY KEY,
  name text,
  last_update datetime
);
CREATE TABLE city (
  city_id integer PRIMARY KEY,
  city text,
  country_id integer,
  last_update datetime
);
CREATE TABLE country (
  country_id integer PRIMARY KEY,
  country text,
  last_update datetime
);
CREATE TABLE customer (
  customer_id integer PRIMARY KEY,
  store_id integer,
  first_name text,
  last_name text,
  email text,
  address_id integer,
  active integer,
  create_date datetime,
  last_update datetime
);
CREATE TABLE film (
  film_id integer PRIMARY KEY,
  title text,
  description text,
  release_year text,
  language_id integer,
  original_language_id integer,
  rental_duration integer,
  rental_rate real,
  length integer,
  replacement_cost real,
  rating text,
  special_features text,
  last_update datetime
);
CREATE TABLE film_actor (
  actor_id integer PRIMARY KEY,
  film_id integer PRIMARY KEY,
  last_update datetime
);
CREATE TABLE film_category (
  film_id integer PRIMARY KEY,
  category_id integer PRIMARY KEY,
  last_update datetime
);
CREATE TABLE inventory (
  inventory_id integer PRIMARY KEY,
  film_id integer,
  store_id integer,
  last_update datetime
);
CREATE TABLE language (
  language_id integer PRIMARY KEY,
  name text,
  last_update datetime
);
CREATE TABLE payment (
  payment_id integer PRIMARY KEY,
  customer_id integer,
  staff_id integer,
  rental_id integer,
  amount real,
  payment_date datetime,
  last_update datetime
);
CREATE TABLE rental (
  rental_id integer PRIMARY KEY,
  rental_date datetime,
  inventory_id integer,
  customer_id integer,
  return_date datetime,
  staff_id integer,
  last_update datetime
);
CREATE TABLE staff (
  staff_id integer PRIMARY KEY,
  first_name text,
  last_name text,
  address_id integer,
  picture blob,
  email text,
  store_id integer,
  active integer,
  username text,
  password text,
  last_update datetime
);
CREATE TABLE store (
  store_id integer PRIMARY KEY,
  manager_staff_id integer,
  address_id integer,
  last_update datetime
);

Hint: 'Nick Wahlberg' is a full name of an actor; full name refers to first_name, last_name; G rating refers to rating = 'G'; calculation = DIVIDE(SUM(rating = 'G'), SUM(rating)) * 100

Question: Among the films starred by Nick Wahlberg, what is the percentage of the films with G rating?

assistant: SELECT CAST(SUM(IIF(T3.rating = 'G', 1, 0)) AS REAL) / COUNT(T3.film_id) FROM actor AS T1 INNER JOIN film_actor AS T2 ON T1.actor_id = T2.actor_id INNER JOIN film AS T3 ON T2.film_id = T3.film_id WHERE T1.first_name = 'Elvis' AND T1.last_name = 'Marx'