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).
Annika is now well below its former popularity. All-time it's been given to 36,398 U.S. babies, the 949th most common name by sound today, peaking at 1,701 in 2003, with 523 in 2025.
By sound, Annika also includes the spellings Anika.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).