Who was the top selling album artist in the 1970s according to billboard?

The best selling album of the entire 1970's was between peter frampton's album or Fleetwood Mac's album rumours. I would say based on what album was spoken the most, proabably rumours by FM. Although Peter's album was close to rumours, but fleetwood mac just sold more albums than ever before when it came out in 77'. So I hope I answered your question.