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).
Steven is now well below its former popularity. All-time it's been given to 2,169,388 U.S. babies, the 353rd most common name by sound today, peaking at 60,174 in 1955, with 2,102 in 2025.
By sound, Steven also includes the spellings Stephen, Stevan.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).