A rough estimate.

(define easy-to-reach-authors
   '((Takashi Kato                  2)
     (Alex Shinn                    4)
     (Amirouche Boubekki            4)
     (Daphne Preston-Kendal         5)
     (Shiro Kawai                   5)
     (Arvydas Silanskas             7)
     (Aubrey Jaffer                 9)
     (Per Bothner                   9)
     (Lassi Kortela                 10)
     (Wolfgang Corcoran-Mathe       10)
     (Marc Feeley                   11)
     (Michael Sperber               14)
     (Marc Nieper-Wißkirchen        34)
     (John Cowan                    53)))

(define easy-to-reach
   (fold + 0 (map last easy-to-reach-authors)))

(define total 246)

easy-to-reach  ; 177

(inexact (/ easy-to-reach total))  ; 70%