Date the Motion Picture Association of America began to rate films:

November 1, 1968
The ratings started at G for "general" and ranged to X for "restricted" to those under 17.
Source: The New York Times, 11/1/1968

 
   
  Movie rating which results in the most profitable movies:

G
According to a study, G movies made an average profit of $78 million between 1989 and 2003, while "R" rated movies generated an average $6.9 million profit.
Source: Atlantic Monthly, 9/1/2005

 
   
  Percentage of American movies from 1989 to 2003 which had an "R" rating :

52%

Source: Atlantic Monthly, 9/1/2005

 
   
  Percentage of American movies released since 1989 which have had a PG rating :

16%
According to a study done by the Dove Foundation.
Source: Atlantic Monthly, 9/1/2005