How to read the band →
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).
Jasper
Jasper has been climbing in recent years. All-time it's been given to 63,674 U.S. babies, the 255th most common name by sound today, peaking at 3,014 in 2023, with 2,845 in 2025.
Jasper has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).