economy-dw

economy-dw.clj

; https://www.scientificamerican.com/article/is-inequality-inevitable/
; https://threadreaderapp.com/thread/1210332075787608065.html

(defn economy-dw
  "
    Simulate one round of
    random transfers of wealth
    between the given agents' accounts
    (a vector of initial amounts)

    e.g.

    (last (take 1000 (iterate economy-dw (vec (repeat 1000 100)))))

    view histogram with Incanter:
    
    (ic/view (ih/histogram (last (take 1000 (iterate economy-dw (vec (repeat 1000 100)))))))
  "
  ([agents]
    (economy-dw {} (vec agents)))
  ([{:keys [wdw ldw] :or {wdw 0.2 ldw -0.17}} agents]
    (reduce
       (fn [r x]
         (let [y (rand-int (count r))
               [a b] (if (< (r x) (r y)) [x y] [y x])
               c (== 1 (rand-int 2))
               dw (* (r a) (if c wdw ldw))]
           (-> r (update a + dw) (update b - dw))))
       agents (range (count agents)))))