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).
Jamie was more common in the past and has since settled at a lower, steady level. All-time it's been given to 559,963 U.S. babies, the 501st most common name by sound today, peaking at 29,850 in 1976, with 1,375 in 2025.
By sound, Jamie also includes the spellings Jaime, Jami, Jayme, Jaimie, Jamey, Jammie, Jaimee, Jaymie, Jamee. Spellings sometimes heard the same way: Jame.