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).
Hayden was more common in the past and has since settled at a lower, steady level. All-time it's been given to 162,812 U.S. babies, the 222nd most common name by sound today, peaking at 9,521 in 2008, with 3,281 in 2025.
By sound, Hayden also includes the spellings Haiden, Haden, Haidyn, Haydn.