The Bee Gees were a pop music group formed in 1958. Their lineup consisted of brothers Barry, Robin, and Maurice Gibb. The trio were successful for most of their decades of recording music, but they had two distinct periods of exceptional success: as a popular music act in the late 1960s and early 1970s, and as prominent performers of the disco music era in the mid-to-late 1970s. The group sang recognisable three-part tight harmonies; Robin's clear vibrato lead vocals were a hallmark of their earlier hits, while Barry's R&B falsetto became their signature sound during the mid-to-late 1970s and 1980s.

At one point in 1978, the Gibb brothers were responsible for writing and/or performing nine of the songs in the Billboard Hot 100. In all, the Gibbs placed 13 singles onto the Hot 100 in 1978, with 12 making the Top 40. The Gibb brothers are fellows of the British Academy of Songwriters, Composers and Authors (BASCA). At least 2,500 artists have recorded their songs.  Singer-songwriter Gavin DeGraw spoke to the Bee Gees' influence with their own music as well as their songwriting:  "Let's talk about the Bee Gees. That's an iconic group. Not just a great band, but a great group of songwriters. Even long after the Bee Gees' success on the pop charts, they were still writing songs for other people, huge hit songs. Their talent went far beyond their moment of normal pop success. It is a loss to the music industry and a loss of an iconic group. The beauty of this industry is that we do pay tribute and every artist coming up is a fan of a generation prior to it, so there's a real tradition element to it".  Among the artists who have covered their songs are Michael Bolton, Boyzone, Eric Clapton, Billy Corgan, Destiny's Child, Faith No More, the Flaming Lips, John Frusciante, Al Green, Engelbert Humperdinck, Elton John, Tom Jones, Janis Joplin, Demi Lovato, Lulu, N-Trance, the Pet Shop Boys, Elvis Presley, Nina Simone, Percy Sledge, Robert Smith, Status Quo, Steps and Take That.  In 2009, as part of the Q150 celebrations, the Bee Gees were announced as one of the Q150 Icons of Queensland for their role as "Influential Artists".

Answer the following question by taking a quote from the article: what was their greatest accomplishment?
At one point in 1978, the Gibb brothers were responsible for writing and/or performing nine of the songs in the Billboard Hot 100.