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).
Joe is now well below its former popularity. All-time it's been given to 645,485 U.S. babies, the 1,424th most common name by sound today, peaking at 14,885 in 1947, with 274 in 2025.
By sound, Joe also includes the spellings Jo.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).