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).
Tanner has been slowly declining from its former popularity. All-time it's been given to 100,166 U.S. babies, the 819th most common name by sound today, peaking at 4,827 in 1998, with 684 in 2025.
Tanner has no common alternate spellings by sound.