Originally Posted by TomSpilsbury:
“The first five episodes in 2005 had amended AIs, released after the initial overnights. These were:
Rose: 76
The End of the World: 76
The Unquiet Dead: 80
Aliens of London: 82
World War Three: 81
After that point, the AI system changed, and the 'overnight' AIs became the only figures issued.”
My understanding is that those aren't amended AIs, but a result of parallel AI systems running for a while. The figures you quote being from the old system, and the other figures, the ones we are used to, being from the new system (from Gfk).
Of course there are timeshift included AIs produced now, which the BBC say tend to produce higher scores, but we don't see them. I think it was only a couple of years ago (maybe three or four?) that Gfk started asking panellists to score things they timeshifted.