The UK Albums Chart is a weekly record chart based on album sales from Sunday to Saturday in the United Kingdom. Albums are defined by the Official Charts Company (OCC) as being a type of music release that features more than four tracks and lasts longer than 25 minutes. During the 1970s, sales of albums in the United Kingdom were compiled on behalf of the British music industry by the British Market Research Bureau (BMRB). Panel sales from approximately 250 (later expanded to 450) representative record stores across the UK were collected each week, and a multiplier figure would then be applied to these panel sales figures to obtain an estimate of the total sales across the country and to compile the weekly chart. Each week's number one was first revealed at 12.45 pm on Thursdays on the lunchtime show on BBC Radio 1, and then moved to 6:05 pm (later 6:30 pm) on Wednesday evenings during the Peter Powell and Bruno Brookes shows. The official charts of the best-selling singles and albums of the 1970s were compiled by BMRB and published in Music Week in the issue dated 22 December 1979, and the top 100 singles and albums were counted down throughout the day on Radio 1 on 31 December 1979, playing one track from each of the top 100 albums. As the charts had to be compiled before the end of the year, the cut-off date for collection of sales data was 8 December 1979. The biggest-selling album of the 1970s in the UK was Bridge over Troubled Water by American duo Simon & Garfunkel. Released on 6 February 1970, it spent a total of 33 weeks at number one, and was the best-selling album of both 1970 and 1971. Originally it was credited with 41 weeks at number one, but this figure includes eight weeks in February and March 1971 when no charts were published due to a postal strike which prevented collection of sales data, and the chart of 30 January 1971 was reused during this period. In 2006 the OCC decided that the rival Melody Maker album chart would replace the missing weeks, with George Harrison's All Things Must Pass at number one during that period. Although it was not an immediate big seller at the time and therefore does not appear in this list, Bat Out of Hell by Meat Loaf has since gone