Kitty Kallen was an American singer who was a genuine star of the 1940s and 50s, fronting big bands and scoring chart-toppers in her day. Her place on this list is a modern, streaming-driven phenomenon rather than a reflection of her career, which included the number-one hit "Little Things Mean a Lot".
Her most-streamed track is "It's Been a Long, Long Time", a tender 1945 ballad of postwar reunion, whose gentle nostalgia has made it a favourite of filmmakers, featuring memorably in superhero films and other productions decades later.
On streaming, "It's Been a Long, Long Time" sits near 166 million plays, while her next most-streamed track trails at under four million. That sends the ratio above 40, far past our 5.0 line.
By our measure Kitty Kallen is a certified one-hit wonder by stream count, with the clear caveat that she was a major recording artist in her own era with more than one hit. It is simply that modern soundtrack placements have gathered the streaming audience around one wartime ballad, which now stands far ahead of the rest of a catalogue most listeners no longer remember.