Series 3 & 4
Series 3 kept steady ratings, the Christmas Special pulling in the highest viewings, with the rest having views between around 6.5 and 8.5 million. The Christmas Special, featuring Kylie Minogue, gathered the highest ratings seen in New Who and Series 4 started off with 9 million viewers before dropping to between 6 and 8 for most of the series. Nearly 9 and then 10.5 million viewers for the last few episodes, more than likely due to David Tennant's surprise regeneration cliffhanger. S3 Average Ratings: 7.54 S4 Average Ratings: 8.04 S3 Average Ratings (Including Christmas Special): 7.67 S4 Average Ratings (Including Christmas Special): 8.42
Both Series 3 and 4 faired better than the previous two when it came to the Appreciation Index. Neither of them fell below 84 with the Series 4 two part finale reaching a score of 91 in both episodes. S3 Average AI: 86.3 S4 Average AI: 88 S3 Average AI (Including Christmas Special): 86.2 S4 Average AI (Including Christmas Special): 87.9