Efficiency drop when joining and splitting teams What will happen when a team is either split or joined with another team?
After reading about Tuckman's stages of group development, I understand that the new team will probably start at the beginning or go back a few stages depending on how much they know each other and how much they have worked together before.

My questions are:


Has there has been done any research on why you should or should not join or merge teams in short time periods?
By how much will the efficiency drop by on average?
How long does it take on average to become as efficient as before?


EDIT: To read more about tuckman's stages of group development you can go to this site. There is also some books written but to get a quick introduction this would suffice.
Has there has been done any research on why you should or should not
  join or merge teams in short time periods?


One big difference in how the troops were maintained in the second world war was that for the allied forces when a person died/got seriously injured this person was always replaced with another one (under the assumption "you always want the troops to be fully staffed"), whereas the Germans did not replace troop members and the troop kept its original staffing until it became too small when it was just broken up (motivated by group dynamics as you are asking about).

It seems at first a bit counter intuitive, but the Germans performed better due to their strategy than just continuously replace personnel. I am sure there exists a lot of research into this.