New Simple Economy 2.0.1

globals [
  gini-index-reserve
  lorenz-points
  Pareto-ratio
]

turtles-own [ wealth ]

to setup
 clear-all
  ask patches [ set pcolor white ]
  create-turtles num-agents [
    ;; everyone starts with the same amount of after-tax money
    set wealth initial-wealths
    set shape "circle"
    set color 125
    set size 3
    ;; visualize the turtles from left to right in ascending order of wealth
    setxy wealth random-ycor  ; all agents have same initial wealth
  ]
    update-lorenz-and-gini
  reset-ticks
end 

to recolor-turtles
  ;; Set the class of the turtles -- if a turtle has less than a third
  ;; the wealth of the richest turtle, color it red.  If between one
  ;; and two thirds, color it green.  If over two thirds, color it blue.

  ; ask turtles [set wealth sort wealth]
  let max-wealth max [wealth] of turtles
  ask turtles
    [ ifelse (wealth <= max-wealth / 3)
        [ set color red ] ; one-third of maximum wealth
        [ ifelse (wealth <= (max-wealth * 2 / 3))  ; two-thirds of maximum wealth
            [ set color green ]
        [ set color blue ] ]
  ]
end 

to go
  ;; agents with less than the transaction amount can't give it away
  ask turtles [if wealth >= transaction-amount [ transact-and-update ]]
  ;; prevent wealthy turtles from moving too far to the right
  ask turtles [ ifelse wealth <= max-pxcor [ set xcor wealth ] [ set xcor wealth * 2]] ; xcor can't exceed max-pxcor
  recolor-turtles
  update-lorenz-and-gini
  tick
end 

to transact-and-update
  ;; prevent rich turtles from going too far to the right
  if wealth >= max-pxcor [ set xcor max-pxcor ]
  ;; give transaction-amount to another turtle
  set wealth wealth - transaction-amount
  ask one-of other turtles [ set wealth wealth + transaction-amount ]
end 

to update-lorenz-and-gini

  ;; this procedure recomputes the value of gini-index-reserve
  ;; and the points in lorenz-points for the Lorenz and Gini-Index plots
  ;; initialize variables before computing Lorenz curve and Gini
  let sorted-wealths sort [wealth] of turtles
  let total-wealths sum sorted-wealths
  let wealth-sum-so-far 0
  let index 0
  set gini-index-reserve 0
  set lorenz-points []

  ;; now actually plot the Lorenz curve -- along the way, we also
  ;; calculate the Gini index.
  ;; (see the Info tab for a description of the curve and measure)
  repeat num-agents [
    set wealth-sum-so-far (wealth-sum-so-far + item index sorted-wealths)
    set lorenz-points lput ((wealth-sum-so-far / total-wealths) * 100) lorenz-points
    set index (index + 1)  ; counts the number of agents in this loop
    set gini-index-reserve gini-index-reserve + (index / num-agents) - (wealth-sum-so-far / total-wealth)
  ]
end 

to-report top-10-pct-wealth
  report sum [ wealth ] of max-n-of (count turtles * 0.10) turtles [ wealth ]
end 

to-report top-20-pct-wealth
  report sum [ wealth ] of max-n-of (count turtles * 0.20) turtles [ wealth ]
end 

to-report bottom-50-pct-wealth
  report sum [ wealth ] of min-n-of (count turtles * 0.50) turtles [ wealth ]
end 

to-report bottom-80-pct
  report sum [ wealth ] of min-n-of (count turtles * 0.80) turtles [ wealth ]
end 

to-report total-wealth
  report sum [ wealth ] of turtles
end 

to-report Pareto-80/20-test
  report ((sum [ wealth ] of min-n-of (count turtles * 0.80) turtles [ wealth ]) - (sum [ wealth ] of max-n-of (count turtles * 0.20) turtles [ wealth ]))
end 

to-report wealth-by-class
  report (sum [ wealth ] of turtles with [ color = red ])
  report (sum [ wealth ] of turtles with [ color = green ])
  report (sum [ wealth ] of turtles with [ color = blue ])
end 

to-report top-wealth-%
  report ((sum [ wealth ] of turtles with [ color = blue]) / (sum [ wealth ] of turtles) * 100)
end 

to-report mid-wealth-%
   report ((sum [ wealth ] of turtles with [ color = green ]) / (sum [ wealth ] of turtles) * 100)
end 

to-report low-wealth-%
   report ((sum [ wealth ] of turtles with [ color = red ]) / (sum [ wealth ] of turtles) * 100)
end 

to-report top-wealth-population
  report (count turtles with [ color = blue ])
end 

to-report mid-wealth-population
  report (count turtles with [ color = green ])
end 

to-report low-wealth-population
  report (count turtles with [ color = red ])
end 

to-report top-average-wealth
   report (((sum [ wealth ] of turtles with [ color = blue ]) / (count turtles)))
end 

to-report mid-average-wealth
   report ((sum [ wealth ] of turtles with [ color = green ]) / (count turtles))
end 

to-report low-average-wealth
   report ((sum [ wealth ] of turtles with [ color = red ]) / (count turtles))
end 

to-report upper-third-wealth
  report sum [ wealth ] of turtles with [ color = blue]
end 

to-report middle-third-wealth
   report sum [ wealth ] of turtles with [ color = green]
end 

to-report lower-third-wealth
   report sum [ wealth ] of turtles with [ color = red]
end