Except that the viewing figures usually given for Doctor Who in the 1960s are the BBC's own internal estimates from the time. These figures often differ significantly from estimates by the agency Total Audience Measurement (TAM), which were until 1968 used by ITV networks and advertisers, and based on numbers of households watching not individual viewers.
|Episode||Tx date||Audience (BBC)||Audience (TAM)|
|1||20 May 1967||8.1 million||4.3 million|
|2||27 May 1967||7.5 million|
|3||3 June 1967||6.1 million|
|4||10 June 1967||5.3 million||under 4.45 million|
|5||17 June 1967||5.1 million|
|6||24 June 1967||6.8 million||3.4 million|
|7||1 July 1967||6.1 millions||2.9 million|
The TAM figures here are taken from The Stage and Television Today issues #4498 (29 June 1967), #4501 (20 July 1967), and #4506 (24 August 1967), where Doctor Who episodes were among the top five most-viewed children's programmes of the preceding month. For episode 4, TAM figures published in issue #4497 (22 June 1967) give the top 20 most-viewed programmes for the week ending 11 June. Doctor Who is not listed but the figure for the 20th most-viewed programme is 4,450,000.
Since 1981, a single, independent measurement of viewing figures has been produced by the Broadcasters Audience Research Board (BARB), but methods of estimating numbers of viewers have evolved over the years so we should be wary of the conclusions we draw from comparing data from different periods. However, it may help contextualise the figures cited above to know that BARB estimates that in January 1967 there were 18 million homes in the UK, 15.9 million of them with TVs; by January 1968 that figure had risen to 18.2 million homes, 16.4 million with TVs. See www.barb.co.uk/resources/tv-ownership/
(This was a footnote cut from my book on The Evil of the Daleks.)