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).
Megan has been slowly declining from its former popularity. All-time it's been given to 615,529 U.S. babies, the 996th most common name by sound today, peaking at 28,853 in 1985, with 403 in 2025.
By sound, Megan also includes the spellings Meghan, Meagan, Meaghan, Maegan, Meghann, Magen, Meggan, Magan.