It's 2005, and Doctor Who is back on the air, 16 years after its 1989 cancellation. And what a difference! Well actually no, not that much to be honest. Although 1963's debut story opened with just over 4 million viewers and quickly climbed to 10 million and above over the next few weeks, and the 2005 revival opened with 10 million but quickly settled down to between 7 and 8 for the next 13 weeks...strangely this means that roughly the same amount of people are watching Series 1 as watched Season 1.
Anyway, making comparisons between the old and the new is almost meaningless now, because 42 years after "An Unearthly Child" it isn't only Doctor Who that has changed. The system of monitoring and recording audience figures has altered drastically, becoming both more accurate and more detailed. TV itself has changed, with far more than the maximum 4 channels of the Classic series, and far higher quality programming. The new series of Doctor Who has to compete with all this, and viewer expectation too. It does it admirably.
The 2005 season of Doctor Who is not referred to as "Season 27" by the BBC (annoying some fans), but rather as "Series 1". It begins on the 26th March 2005 and finishes on the 18th June. At 13 weeks it ties with Season 22 for the shortest season of Doctor Who, but this is now the norm as the rigours of 9 months worth of filming mean that this is the most Doctor Who that can be produced in a single year.
(Let me clarify this. Although one could argue for hours about the difference between the two terms, and the fact that a Season tends to indicate a single run of programmes within a larger overall Series...practically I follow the BBC's lead here - the Classic Series consists of 26 annual Seasons, whereas the New Series consists of so far 9 annual....Series).
Since the audience now has the capability to record TV programmes and play them back later (not only the VCRs of the 80s, but DVD and Hard Disk recorders, SKY boxes, TIVO) We now have "Overnight" and "Final" viewing figures. Together with repeats on minor digital channels, and each episode available to stream or download from BBC IPlayer for a month after, it is increasingly difficult to "miss" a TV programme, and so more people are choosing to record and watch later.
The difference between the Overnight audience and the Final audience is traditionally referred to as the "Timeshift", and is the most significant difference not only between "Classic" and "New" Who, but also between individual "New" seasons. The average Timeshift for Doctor Who Series 1 is 7.9%. This means that of the total number of viewers up to 7 days after transmission, approximately 92% are still watching it "on the night".