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).
Mariah has been slowly declining from its former popularity. All-time it's been given to 135,341 U.S. babies, the 628th most common name by sound today, peaking at 5,988 in 1996, with 989 in 2025.
By sound, Mariah also includes the spellings Moriah, Mariyah. Spellings sometimes heard the same way: Maria.