The graph above shows the age groups that view adult film (rated 15+) GAP is what is predicted to view, and universe is the actual viewing. It shows the people that they are aiming the films at when they are being produced, etc. This is categorising by adult age groups.
This graph shows the age groups of people who go to view family films, so those films rated 'U', or 'PG'. This is the reason this graph goes down to the age of 7, rather than 15, as 7 is the recommended age for the viewing of films rated 'U'.
This is how they categorise films into age groups, by looking at these charts, and seeing who really goes to see what!
These graphs were from the following link...