The Timeshift is the difference between viewers who watched on the night and viewers who watched up to 7 days later, expressed as a percentage of Total viewers. The figures above tell us more about how Television has changed between 2005 and 2014 than about Doctor Who. The huge jump for Series 5 does seem to coincide with SKY supplying SKY+ HD boxes as standard from January 2010 onwards. This will have resulted in more people getting access to SKY recording technology and HD broadcasts.
Why the slight dip between Series 1, 2 and 3? Who knows? Statistically it's not much of a drop, only 1 or 2%. But it does indicate that slightly more people were watching On The Night than the previous year. Perhaps ITV weren't running phone-in's opposite Who for those years, but without knowing exactly what, it's difficult to tell. But the increase to today's 25% of viewers choosing to watch later is inescapable.
Well since I wrote that (towards the end of 2013) Series 8, 9 and 10 have finished. This time in 2014 fans were panicking about the low overnight figures (around 5 million) for the last few stories. In 2015 they were panicking about the even lower overnights for Series 9. But look at the Timeshift.
Series 8 averaged 28.9% (with a 31.5% peak for "Listen"), Series 9 averaged slightly higher at 29.3% (with a 35% peak for "The Witch's Familiar"), while Series 10 averaged just over 30% (with a peak of 38.9% for "The Eaters of Light"). I think we can finally conclude that this is how TV is changing, and in fact how TV has changed, as this is not a phenomenon unique to Doctor Who. Increasingly Event Television is watched on the night, while Serial Television is recorded and watched later. Interestingly, a look at the above graph does show that while Timeshift has steadily increased since 2008, the increase between 2015 and 2014 is much smaller. It's tempting to speculate that we may be approaching a Timeshift plateau, and so long as the mix of Event and non-Event TV remains the same, 30% Timeshift is the highest we may see.
-Spacewarp July 2017