Simple Economy Updated

;; Modified and detailed commented by 深度碎片
;; originally written by Uri Wilensky

;; Background of this model, quotes from Wilensky's book at https://github.com/EmbraceLife/shendusuipian/issues/51
;; concept for analyzing this model at https://github.com/EmbraceLife/shendusuipian/issues/53
;; updated model at https://github.com/EmbraceLife/NetLogo-Modeling/tree/master/finished%20models

;; What are the basic rules created such exponential inequality?
;; rules ;; 1. total wealth stays the same;
;; rules ;; 2. the population stays the same;
;; rules ;; 3. each agent has the same initial wealth;
;; rules ;; 4. each iteration, for any one of the agents gives away 1 dollar, and one other agent receives one dollar

;; insights ;; a great example of making assumptions to build a simple model


             ;; globals, properties, classes
globals [

  top-20pct     ;; top 20% agents in wealth

  bottom-20pct  ;; bottom 20% agents in wealth

]

turtles-own [

  wealth        ;; wealth as new property to agent
]

to setup                                                                        ;; build the world

  clear-all                                                                        ;; wipe out everything

  create-turtles 500 [                                                             ;; create 500 agents, ask each to do the following

    set wealth 100                                                                    ;; has wealth of 100

    set color green                                                                   ;; color itself green

    set shape "circle"                                                                ;; make itself circle-like

    set size 2                                                                        ;; make itself twice big

    setxy wealth random-ycor                                                          ;; put itself horizontally based on wealth and vertically with random
  ]


  reset-ticks                                                                         ;; set clock to 0
end 

to go                                                                            ;; running the world

  ask turtles with [ wealth > 0 ] [                                                 ;; ask all agents with positive wealth to do

    transact                                                                           ;; transact money to each other
  ]


  ask turtles [                                                                     ;; ask all agents

    ifelse wealth <= max-pxcor                                                         ;; if wealth is not over the board (set board long enough )

      [ set xcor wealth ]                                                                 ;; stay horizontally where its wealth is

      [ set xcor max-pxcor set size 1.5 ]                                                 ;; otherwise, stay horizontal at the border edge and make self twice big

  ]


  plot-wealth-gap                                                                 ;; plot the wealth gap between the top 20% vs the bottom 80%


  plot-wealth-distribution                                                        ;; plot wealth distribution of the population



  if track? [                                                                     ;; click on track to execute once

    set top-20pct max-n-of (count turtles * 0.2) turtles [wealth]                    ;; get the top 20% agents at this moment

    ask top-20pct [
        set color red set size 3                                                     ;; ask them to be red and triple in size
    ]

    set bottom-20pct min-n-of ( count turtles * 0.2 ) turtles [wealth]               ;; get the bottom 20% agent at this same moment

    ask bottom-20pct [
        set color blue set size 3                                                    ;; ask them to be red and triple in size
    ]


    set track? false                                                                 ;; make sure track only happen once

  ]

  if top-20pct != 0 and any? top-20pct [                                          ;; if top-20pct agents do exist ( not 0 not empty )

    let top-20-now max-n-of (count turtles * 0.2) turtles [wealth]                   ;; get current top-20pct agents in wealth

    let min-top-20 min [wealth] of top-20-now                                        ;; get the minimum wealth value  of the current top-20pct agents

    let num-reach-top-20 count top-20pct with [wealth > min-top-20]                  ;; count the number of agents of top-20pct who belong to current top-20pct

    let pct-reach-top-20 num-reach-top-20 / count top-20pct * 100                    ;; calc its ratio of original top-20pct

    let top-40-now max-n-of (count turtles * 0.4) turtles [wealth]
    let min-top-40 min [wealth] of top-40-now
    let num-reach-top-40 count top-20pct with [wealth > min-top-40]
    let pct-reach-top-40 num-reach-top-40 / count top-20pct * 100                    ;; calc the ratio of original top-20pct which belong to current top-40pct

    let top-50-now max-n-of (count turtles * 0.5) turtles [wealth]
    let min-top-50 min [wealth] of top-50-now
    let num-reach-top-50 count top-20pct with [wealth > min-top-50]
    let pct-reach-top-50 num-reach-top-50 / count top-20pct * 100                    ;; calc the ratio of original top-20pct which belong to current top-50pct

    plot-top20pct-stability pct-reach-top-20 pct-reach-top-40 pct-reach-top-50       ;; plot the three ratios above

  ]

  if bottom-20pct != 0 and any? bottom-20pct [                                    ;; if bottom-20pct agents do exist (not 0 not empty)

    let bottom-20-now min-n-of (count turtles * 0.2) turtles [wealth]                ;; get current bottom 20pct agents in wealth

    let max-bottom-20 max [wealth] of bottom-20-now                                  ;; get the maximum wealth value of the current bottom 20pct agent

    let num-above-bottom-20 count bottom-20pct with [wealth > max-bottom-20]         ;; count the number of agents in original bottom 20pct go above current bottom 20pct

    let pct-above-bottom-20 num-above-bottom-20 / count bottom-20pct * 100           ;; calc the ratio of original bottom-20pct


    let bottom-40-now min-n-of (count turtles * 0.4) turtles [wealth]
    let max-bottom-40 max [wealth] of bottom-40-now
    let num-above-bottom-40 count bottom-20pct with [wealth > max-bottom-40]
    let pct-above-bottom-40 num-above-bottom-40 / count bottom-20pct * 100           ;; calc the ratio of original bottom-20pct which stay above to current bottom-40pct

    let bottom-50-now min-n-of (count turtles * 0.5) turtles [wealth]
    let max-bottom-50 max [wealth] of bottom-50-now
    let num-above-bottom-50 count bottom-20pct with [wealth > max-bottom-50]
    let pct-above-bottom-50 num-above-bottom-50 / count bottom-20pct * 100           ;; calc the ratio of original bottom-20pct which stay above to current bottom-50pct

    plot-bottom20pct-stability pct-above-bottom-20 pct-above-bottom-40 pct-above-bottom-50  ;; plot the three ratios above

  ]


  tick
end 

to transact                                                                       ;; transact wealth

  set wealth wealth - 1                                                              ;; give away 1 unit of wealth

  ask one-of other turtles [ set wealth wealth + 1 ]                                 ;; another agent receive 1 unit of wealth
end 

to-report top-20-pct-wealth                                                       ;; report wealth sum of top 20pct agent to `top-20-pct-wealth`

  report sum [ wealth ] of max-n-of (count turtles * 0.2) turtles [ wealth ]
end 

to-report bottom-80-pct-wealth                                                     ;; report wealth sum of bottom 80pct agent to `bottom-80-pct-wealth`

  report sum [ wealth ] of min-n-of (count turtles * 0.8) turtles [ wealth ]
end 

to plot-wealth-gap

  set-current-plot "wealth gap"
  set-current-plot-pen "top 20%"
  plot top-20-pct-wealth
  set-current-plot-pen "bottom 80%"
  plot bottom-80-pct-wealth
end 

to plot-wealth-distribution
 set-current-plot "wealth distribution"
 set-plot-y-range 0 40
 set-current-plot-pen "dist"
 histogram [ wealth ] of turtles
end 

to plot-top20pct-stability [ top20 top40 top50 ]

  set-current-plot "top-20pct-stability"
  set-current-plot-pen "stay top 20"
  plot top20
  set-current-plot-pen "stay top 40"
  plot top40
  set-current-plot-pen "stay top 50"
  plot top50
end 

to plot-bottom20pct-stability [ bottom20 bottom40 bottom50 ]

  set-current-plot "bottom-20pct-stability"
  set-current-plot-pen "above bottom 20"
  plot bottom20
  set-current-plot-pen "above bottom 40"
  plot bottom40
  set-current-plot-pen "above bottom 50"
  plot bottom50
end