In the pattern now set for the rest of the 1970s, Doctor Who's 8th Season ends on the 19th June 1971, and the 9th Season begins on the 1st of January 1972, 27 weeks later.
Is it possible that this rather severe reduction in Doctor Who on TV is paying dividends? Season 9 kicks off with Jon Pertwee's first exciting encounter with the Daleks, a four-parter that sees viewing figures climb from 9.8 million to 10.4, dropping no lower than 9.1 during the first 4 weeks. The next story, "The Curse of Peladon" sees viewers start at a very respectable 10.3 million, peak at 11 a week later but then inexplicably drop to round the 7 million mark.
Actually this is one drop in viewership we do know the reason for (and I for one actually remember it). The UK at this time was suffering from power cuts due to the first of many miners' strikes. These cuts were regular, scheduled, and began in February, right in the middle of "Curse". The strike only lasted 9 days (although the cuts lasted slightly longer) and viewing figures appear to have stabilised by the middle of "The Sea Devils".All in all Season 9 appears reasonably well-attended by viewers, and to be honest conforms to what we still see in Doctor Who to this day - the season starts off on a high, which settles down into a core of steady viewership, and ends either slightly higher or on the same level. Season 9 is no different. Stories peak at around 8 million, and trough at around 7.5, but rarely go higher or lower than these. In fact you could overlay Season 9 onto Season 8 and not notice much difference. It is tempting to speculate that some combination of the 3rd Doctor, the new format of the series, or the reduction in episodes has led to this.
Approximately 1-2 million more viewers seem to regularly appreciate Doctor Who than they did during Season 6...but this does not mean that Season 9 is an unprecedented success. Seasons 1 and 5 were comparable to this, and Season 2 beat it hands down in places. Though the one thing we do notice about viewing figures during the 3rd Doctor's era, compared to the 1st's, is that they are far more stable.