Summary of change in length of career and bouts across eras
| Fight era | N | References | Average career length (years) | Range (years) | Average bouts | Range |
|---|---|---|---|---|---|---|
| 1900–1955 | 254 | 3, 10, 15, 16 | 19 | 3–22 | 336.5 | <50–700+ |
| 1950–1995 | 77 | 17, 18, 19 | 9.6 | 1–22 | 39.6 | 0–122 |
| 2000 – present | 295 | 9, 20 | 5 | 1–32 | 13.3 | 1–138 |