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).
Marley has stayed fairly steady in American naming for generations. All-time it's been given to 66,980 U.S. babies, the 334th most common name by sound today, peaking at 4,100 in 2008, with 2,072 in 2025.
By sound, Marley also includes the spellings Marlee, Marleigh, Marlie.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).