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).
Bruce was more common in the past and has since settled at a lower, steady level. All-time it's been given to 388,275 U.S. babies, the 1,000th most common name by sound today, peaking at 14,693 in 1956, with 558 in 2025.
Bruce has no common alternate spellings by sound.