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).
Benson has stayed fairly steady in American naming for generations. All-time it's been given to 14,344 U.S. babies, the 852nd most common name by sound today, at an all-time high of 1,227 in 2025.
Benson has no common alternate spellings by sound.