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).
Madilyn has been slowly declining from its former popularity. All-time it's been given to 35,064 U.S. babies, the 589th most common name by sound today, peaking at 1,734 in 2014, with 977 in 2025.
By sound, Madilyn also includes the spellings Madilynn.