I let replacement characters enter game at half experience of the most experienced character. Over time the player with a character loss will end a few levels behind the lead, but it find the competence levels in balance. A 9 level difference sounds like it is hard to handle.
Hmm..it does look a little harsh when you look at the raw figures. here's how it happened:
The (mode and median) average group level is 18.
The highest level character has been played from the very begining of the campaign, i.e., the player has never lost a character during this campaign.
The highest level character has a +10% bonus to all XP via 'exceptionl stat pick' from the memory stat.
The highest level character is played by someone who has missed perhaps 3 or 4 sessions throughout the entire campaign.
The highest level character has participated in her 'personal quest' - Something I do that combines the character's background with personal goals and allows a +10% XP bonus whilst on such adventures.
The highest level character has 'used a magical item' that bestowed a one time +10.000 XP bonus
The lowest (level 13) level character is the second character the player has had during this campaing (which left him 1 level below the lowest party member).
The lowest level character is played by a retail security guard, he plays around 3 weeks in 6, therefore gaining 50% party XP when he is absent.
The lowest level character has not participated in his 'personal quest'
The lowest level character has not 'used a magical item' that bestows a one time +10.000 XP bonus, as it has the additional effect of healing all wounds (plus Lifegiving), once per character (Holy Grail) and has therefor decided to wait until he needs it.
So, as you can see, there are reasons for the gap and the players are so experienced that although the level gap may seem huge, they do not only copr, but also fully understand.