How to read the band →
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).
Pierce
Pierce climbed for decades and has been a steadily popular name ever since. All-time it's been given to 20,634 U.S. babies, the 955th most common name by sound today, peaking at 668 in 2015, with 618 in 2025.
Pierce has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).