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).
Donna is now well below its former popularity. All-time it's been given to 839,891 U.S. babies, the 2,238th most common name by sound today, peaking at 36,707 in 1959, with 98 in 2025.
By sound, Donna also includes the spellings Dawna. Spellings sometimes heard the same way: Dana.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).