Article: Soft rock reached its commercial peak in the mid-to-late 1970s with acts such as Toto, England Dan & John Ford Coley, Air Supply, Seals and Crofts, America and the reformed Fleetwood Mac, whose Rumours (1977) was the best-selling album of the decade. By 1977, some radio stations, like New York's WTFM and NBC-owned WYNY, had switched to an all-soft rock format. By the 1980s, tastes had changed and radio formats reflected this change, including musical artists such as Journey. Walter Sabo and his team at NBC brought in major personalities from the AM Band to the FM Band taking the format from a background to a foreground listening experience. The addition of major radio stars such as Dan Daniel, Steve O'Brien, Dick Summers, Don Bleu and Tom Parker made it possible to fully monetize the format and provide the foundation for financial success enjoyed to this day

Question: In what year was the best selling album of the 1970s released?
1977