Solid line = floor (spellings that unambiguously belong to the group). Shaded band up to the dashed edge = ceiling (the most it could reach if every ambiguous spelling counted here).
Jane was more common in the past and has since settled at a lower, steady level. All-time it's been given to 410,149 U.S. babies, the 563rd most common name by sound today, peaking at 10,520 in 1947, with 1,440 in 2025.
By sound, Jane also includes the spellings Jayne.