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).
Harold was more common in the past and has since settled at a lower, steady level. All-time it's been given to 554,280 U.S. babies, the 1,616th most common name by sound today, peaking at 14,230 in 1924, with 230 in 2025.
Harold has no common alternate spellings by sound.