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).
Kaia has been climbing in recent years. All-time it's been given to 42,691 U.S. babies, the 349th most common name by sound today, peaking at 2,452 in 2023, with 2,162 in 2025.
By sound, Kaia also includes the spellings Kaiya, Kya, Kiah, Kyah. Spellings sometimes heard the same way: Kaya, Kiya.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).