For those interested, Disney used to have a three-tiered system for ages when WDW opened in 1971 -- child (3-11), junior (12-17), and adult (13 and over). It dropped the junior designation in 1984, when it made children 3-12, and then changed the child ticket only three years later, to 3-9, in 1987.

The child ticket has always been only a few dollars less per day than the adult ticket, ranging anywhere from around $2 to $9 per day. However, that amounted to a much greater percentage difference in the past.

This info was gathered from another "website which shall not be named," which has an incredibly detailed history of WDW tickets. To find it, Google search "WDW ticket history."