Calculating rate of change in Clojure

Code

;; rate_of_change.clj

(def numbers [100 107 106 104 111 108 112])

(defn rate-of-change [a b]
  (float (* (/ (- b a) a) 100)))

(rate-of-change 100 107)
;;=> 7.0

(map rate-of-change numbers (rest numbers))
;;=> (7.0 -0.93457943 -1.8867924 6.730769 -2.7027028 3.7037036)

(map + '(1 2 3) '(4 5))
;;=> (5 7)

(map + '(1 2 3) '())
;;=> ()