The last song written by one woman to reach the No. 1 was - 19 years ago

The last song written by just one songwriter to reach the No. 1 at the Billboard Hot 100 was Ed Sheeran’s 'Perfect' in December 2017. The last song written by a solitary female songwriter to reach No. 1 was Alicia Keys’ 'Fallin’' in August 2001. In the 1970s almost half the songs reaching No. 1 were written by just one person. Billboard wonders why and how has it come to this.