Defined age groups:

A 'Single Age Group' is one where only one number resides in that group.  This would be basically all longshots, and even some that are not longshots. An example is age slot 54 - which as only #1 in it, another example is age slot 9 - which has only #24 in it.

A '5 age group' is defined as a group that has 5 numbers in it to choose from, the very last game has 5 to choose from, and the prior 3 games to that - all of them have 5 numbers to choose from because NONE of those numbers have been hit in subsequent games.

There are no '4 Age groups' at the present time, a rarity. There are usually 1 or 2 of them.

'3 Age Group' - there are two of them - one from 7 games ago, and one from 16 games ago, a rarity to have so few, there is usually about 5-6 of them. 

'2 Age Groups' - there are currently 5 of them. 

'Single Age Groups' - there are 19 of them. There are usually 12 or 13.