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).
Austin is down from its peak but still widely used. All-time it's been given to 466,828 U.S. babies, the 184th most common name by sound today, peaking at 27,095 in 1995, with 3,544 in 2025.
By sound, Austin also includes the spellings Austyn, Austen, Auston.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).