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).
Robert
Robert has been easing down from its peak but is still widely used. All-time it's been given to 4,869,849 U.S. babies, the 186th most common name by sound today, peaking at 91,892 in 1947, with 3,777 in 2025.
Robert has no common alternate spellings by sound.
Rising