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).
Shea has stayed fairly steady in American naming for generations. All-time it's been given to 44,909 U.S. babies, the 782nd most common name by sound today, peaking at 1,119 in 1998, with 696 in 2025.
By sound, Shea also includes the spellings Shay, Shae, Shaye. Spellings sometimes heard the same way: Shai.