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).
Stephanie has been slowly declining from its former popularity. All-time it's been given to 829,292 U.S. babies, the 818th most common name by sound today, peaking at 27,425 in 1990, with 684 in 2025.
By sound, Stephanie also includes the spellings Stefanie, Stephany, Stefani, Stephenie, Stephani, Stefany, Stephaine, Steffanie. Spellings sometimes heard the same way: Estefany.