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).
Banks has been climbing in recent years. All-time it's been given to 6,970 U.S. babies, the 649th most common name by sound today, peaking at 1,188 in 2025, with 1,188 in 2025.
Banks has no common alternate spellings by sound.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).