A couple of comments The information is sourced as given from a presumably well researched Gould biography Undoubtedly the album has sold many more copies since his death and those figures are as of and times have changed in the music industry I m not sure it s meaningful to compare sales of this album in a 20 year span ending before the artist s death with the entire catalog of a top conductor I agree that the numbers could be wrong but the answer is to find other information You are welcome to edit astonishing a quote from the source to simply high for example