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).
Jason has dropped sharply from its peak but is still widely used. All-time it's been given to 1,103,214 U.S. babies, the 246th most common name by sound today, peaking at 56,811 in 1977, with 2,743 in 2025.
By sound, Jason also includes the spellings Jayson, Jasen, Jaysen, Jacen.