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).
Janice was a common American name in the 1940s but is rarely given today. It's been given to 456,620 U.S. babies all time and once ranked 212th by sound, peaking at 18,658 in 1947 (down to 80 in 2025).
By sound, Janice also includes the spellings Janis.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).