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).
Kenzie has been slowly declining from its former popularity. All-time it's been given to 33,233 U.S. babies, the 906th most common name by sound today, peaking at 1,746 in 2014, with 471 in 2025.
By sound, Kenzie also includes the spellings Kinsey, Kenzi.