;;; We declare the global variables, available by all the agents and that can be used anywhere in the model. globals [ initial-interest-rate previous-year-rate annual-rate ;;; Euribor, the annual interest rate underwrited by the agents that rise a floating interest rate loan. fixed-annual-rate ;;; The annual interest rate underwrited by the agents that rise a fixed interest rate loan. monthly-rate ;;; Both annual interest rates transformed in monthly interest rates. n.borrowers ;;; Number of new borrowers created every tick according to some conditions. blue-number ;;; The number of agents that have risen a floating interest rate loan positioned on the left side of the monitor each time. green-number ;;; The number of agents that have risen a fixed interest rate loan positioned on the right side of the monitor each time. real-estate-value n.insolvents ;;; Borrowers that result insolvent during the life of the loan. value-effect ;;; The interaction between the real estate value and the number of new borrowers created each time. n.insolvents-effect ;;; The interaction between the number fo insolvent agents and the real estate value each time. n.borrowers-effect ;;; A particular interaction between the number of new borrowers generated each time and the real estate value. exponent ;;; The exponent used to calculate the monthly instalment. ] ;;; We declare the variables belonging to each agent. turtles-own [ initial-endowment monthly-income consumption money debt/value ;;; The real estate value that each agent want to purchase is equal to the entity of loan. monthly-instalment capital-share interest-share residual-debt n.instalments n.instalments-paid capital-share-paid interest-share-paid total-cost ;;; The sum of capital shares paid and the interest shares paid. insolvency ;;; The difference between the entity of loan required and the capital shares paid until the insolvency. interest ;;; The interest rate underwrited by each agent for the loan. ] ;;;;;;;;;;;;;;; ;;;; SETUP ;;;; ;;;;;;;;;;;;;;; to setup clear-all set previous-year-rate (4 + random-float (6)) ;;; The previous year interest rate is randomly generated in the range 4% - 10%. set initial-interest-rate (4 + random-float (6)) ;;; The initial interest rate is randomly generated in the range 4% - 10%. set fixed-annual-rate initial-interest-rate ;;; At the beginning the fixed annual rate and the annual rate are equal to the initial interest rate. set annual-rate initial-interest-rate set n.borrowers 100 - int (beta-interest/n.borrowers * ((initial-interest-rate - previous-year-rate )/ previous-year-rate) * 100) ;;; The initial number of borrowers is inversely proportional set n.insolvents count turtles with [color = red] ;;; It defines the number of insolvent agents every tick. ;;; (according to the beta value choosen by the user) set real-estate-value initial-debt ;;; Every loan required is equal to the real estate value at that moment. ;;; to the relative variation between the initial interest rate and that of a previous year. if initial-interest-rate < previous-year-rate [ ;;; If interest rates go down, the model creates more floating borrowers than fixed borrowers. create-turtles-blue ;;; Turtles blue represent the agents that rise a floating interest rate loan. ] if initial-interest-rate > previous-year-rate [ ;;; If interest rates go up, the model creates more fixed borrowers than floating borrowers. create-turtles-green ;;; Turtles green represent the agents that rise a fixed interest rate loan. ] setup-turtles do-plots-interest-rate do-plots-real-estate do-plots-borrowers do-plots-insolvents end to create-turtles-blue set blue-number int (n.borrowers * 0.7) ;;; Floating borrowers represent the majority (70%) of the new borrowers because the interest rate go down. set green-number n.borrowers - blue-number ;;; Fixed borrowers represent the minority (30%) of the new borrowers in this case. end to create-turtles-green set green-number int (n.borrowers * 0.7) ;;; Fixed borrowers represent the majority (70%) of the new borrowers because the interest rate go up. set blue-number n.borrowers - green-number ;;; Floating borrowers represent the minority (30%) of the new borrowers in this case. end to setup-turtles ;;; Procedure to create the agents and to fix their own initial features. set-default-shape turtles "person" ;;; It modifies the shape of turtles in "person". create-turtles blue-number [ set size 1 set color blue set interest annual-rate ;;; The floating borrowers pay the annual rate (Euribor). set monthly-income ( min-income + random (max-income - min-income) )/ 12 ;;; The monthly income of each agent is randomly generated in a range of income. set initial-endowment endowment/income * monthly-income * 12 ;;; The initial endowment is proportional to the annual income (according to the proportion choosen by the user). set consumption consumption/monthly-income * monthly-income ;;; The monthly consumption is proportional to the monthly income (according to the proportion choosen by the user). set money initial-endowment ;;; The money is equal to the initial endowment. set n.instalments initial-years * 12 ;;; It transforms the life of the amortization plan express in years into a number of mounthly instalments. set n.instalments-paid 1 ;;; Advance payment. set residual-debt initial-debt - capital-share-paid set debt/value initial-debt create-instalment set xcor (-3 - random 13) set ycor random-ycor ;;; All the floating borrowers are randomly positioned on the left side of the monitor. ] create-turtles green-number [ set size 1 set color green set interest fixed-annual-rate ;;; The fixed borrowers pay the fixed annual rate that is the first annual rate generated when they rise the contract, remaining constant until the time to maturity of the loan. set monthly-income ( min-income + random (max-income - min-income) )/ 12 set initial-endowment endowment/income * monthly-income * 12 set consumption consumption/monthly-income * monthly-income set money initial-endowment set n.instalments initial-years * 12 set n.instalments-paid 1 set residual-debt initial-debt - capital-share-paid set debt/value initial-debt create-instalment set xcor (3 + random 13) set ycor random-ycor ;;; All the fixed borrowers are randomly positioned on the right side of the monitor. ] ask turtles [ if n.instalments-paid = 1 and (monthly-income - consumption - monthly-instalment) < 0 [ ;;; All the agents that are unbankable set color white ;;; according to their own features (monthly-instalment, set xcor ( - 2 + random 5) set ycor random-ycor ;;; monthly-income and consumption) ] ;;; change their color in white and move in the centre. ] ask turtles with [color = blue] [ if n.instalments-paid > 1 [ if monthly-income - monthly-instalment - consumption < 0 and monthly-instalment < money [ ;;; If the difference monthly income - monthly instalment - consumption set money money + monthly-income - monthly-instalment - consumption ;;; is negative but the money is congruous, all borrowers ] ;;; continue to pay. if monthly-income - monthly-instalment - consumption < 0 and monthly-instalment > money [ ;;; If also the money is not enough to pay the instalment, set color red ;;; the borrowers are insolvent and change their color in red. set money 0 set insolvency debt/value - capital-share-paid ] ] ] ask turtles [ if n.instalments-paid = 1 and color = green [ ;;; These are the values of each variables if the agents have just risen the contract set fixed-annual-rate annual-rate ;;; (green and blu): the condition "if" is linked to the payment of the first instalment. set debt/value real-estate-value set residual-debt debt/value - capital-share-paid set n.instalments int (initial-years * debt/value / initial-debt) * 12 ] if n.instalments-paid = 1 and color = blue [ set interest annual-rate set debt/value real-estate-value set residual-debt debt/value - capital-share-paid set n.instalments int (initial-years * debt/value / initial-debt) * 12 ] if n.instalments-paid > 1 and color = blue [ set interest annual-rate ] ] end to create-instalment ;;; Procedure that calculates the monthly instalment (according to the french amortization plan). set monthly-rate (1 + (interest + spread) / 100) ^ ( 1 / 12) - 1 ;;; The interest rates are transformed into monthly rates to calculate the periodic instalments that borrowers have to pay. set exponent int(n.instalments - n.instalments-paid ) set monthly-instalment (( monthly-rate *(1 + monthly-rate )^ exponent)/ (((1 + monthly-rate )^ exponent)- 1 )) * residual-debt set interest-share residual-debt * ( monthly-rate ) set capital-share monthly-instalment - interest-share set residual-debt residual-debt - capital-share set total-cost total-cost + monthly-instalment set capital-share-paid capital-share-paid + capital-share set interest-share-paid interest-share-paid + interest-share end ;;;;;;;;;;;; ;;;; GO ;;;; ;;;;;;;;;;;; to go create-interest-rate ask turtles [ if color != red [ create-next-instalment ] ] create-new-turtles create-real-estate-value set n.insolvents count turtles with [color = red] every 1.0 [ ask turtles with [color = red] [die]] ;;; The insolvent agents (color red) disappear from the monitor every 1.0 second. do-plots-interest-rate do-plots-real-estate do-plots-borrowers do-plots-insolvents tick end to create-interest-rate ;;; Procedure that simulates randomly the Euribor's pattern. if random 100 < 50 [ ;;; With probability 1/2 the Euribor is equal to the sum of the last level set annual-rate annual-rate + random-float 0.3 ;;; generated and a random number between 0 e 0.3. if annual-rate > 10.0 [ ;;; Maximum annual rate value (10%). set annual-rate annual-rate - 0.1 ] ] if random 100 >= 50 [ ;;; With probability 1/2 the Euribor is equal to the difference of the last level set annual-rate annual-rate - random-float 0.3 ;;; generated and a random number between 0 e 0.3. if annual-rate < 4.0 [ ;;; Minimum annual rate value. set annual-rate annual-rate + 0.1 ] ] end to create-next-instalment ;;; Procedure to create the instalments next the first. if n.instalments-paid = n.instalments - 1 [die] ;;; When the borrowers finished to pay the debt, they disappear from the monitor. if n.instalments-paid < n.instalments - 1 [ set monthly-rate (1 + (interest + spread) / 100)^ (1 / 12) - 1 set n.instalments-paid n.instalments-paid + 1 create-instalment ] if color = white [die] ;;; The unbankable agents (color white) disappear from the monitor. if monthly-income - monthly-instalment - consumption < 0 and monthly-instalment < money [ ;;; The necessary condition for each agents to use their money. set money money + monthly-income - monthly-instalment - consumption ] end to create-new-turtles ;;; Procedure to create new borrowers during the simulation. set value-effect int (beta-value/n.borrowers * ((real-estate-value - initial-debt)/ initial-debt) * 100) ;;; It defines the real estate value effect on the number of new borrowers generated (according to the beta value choosen by the user). if (add-real-estate-value-effect? = false) [set value-effect 0] ;;; If the relative switch is off the value effect is eliminated from the simulation. if annual-rate < max-accettable-interest [ ;;; Necessary condition to create new borrowers each time (according to the level of maximum accettable interest rate choosen by the user). set n.borrowers ( - int (beta-interest/n.borrowers * ((annual-rate - initial-interest-rate )/ initial-interest-rate) * 100) + value-effect );;; It defines the number of new borrowers each time according to the interest rates effect and the real estate value effect. if n.borrowers < 0 [ ;;; In this case the model doesn't generate any new borrower. set n.borrowers 0 set blue-number 0 set green-number 0 ] if annual-rate < initial-interest-rate [ create-turtles-blue ] if annual-rate > initial-interest-rate [ create-turtles-green ] setup-turtles ask turtles [ create-next-instalment ] ] if annual-rate > max-accettable-interest [ ;;; In this case the model doesn't generate any new borrower. set n.borrowers 0 set blue-number 0 set green-number 0 ] if real-estate-value <= min-desirable-real-estate-value [ ;;; Optional condition to create new borrowers according to the possible collapse of the real estate value. set n.borrowers n.borrowers - value-effect if annual-rate < initial-interest-rate [ create-turtles-blue ] if annual-rate > initial-interest-rate [ create-turtles-green ] setup-turtles ask turtles [ create-next-instalment ] ] end to create-real-estate-value ;;; Procedure that simulates the real estate value according to the interest rates value, the number of insolvents and the number of new borrowers. if (add-n.insolvents-effect? = false)[ ;;; If the relative switch is off the insolvents effect on the real estate value is eliminated from the simulation. set n.insolvents-effect 0 ] if (add-real-estate-value-effect? = false) [ ;;; If the relative switch is off the new borrowers effect, in the case of collapse of real estate value, is eliminated from the simulation. set n.borrowers-effect 0 ] set n.insolvents-effect n.insolvents * 100 ;;; It defines the insolvents effect on the real estate value: a lost of value equal to 100 euro for each insolvent. set real-estate-value initial-debt - (beta-interest/value * ((annual-rate - initial-interest-rate) / initial-interest-rate) * initial-debt) + n.borrowers-effect - n.insolvents-effect if real-estate-value <= min-desirable-real-estate-value [ set n.borrowers-effect n.borrowers * 100 ;;; It defines the new borrowers effect on the real estate value: a gain of value equal to 100 euro for each new borrower. ] if real-estate-value <= (initial-debt / 2 + 1000 + random 2000) [ ;;; It defines the range of value in which the real estate value have to stay. set real-estate-value initial-debt / 2 + 1000 + random 2000 ] if real-estate-value >= (initial-debt * 2 + 1000 + random 2000) [ set real-estate-value initial-debt * 2 - 1000 - random 2000 ] end ;;;;;;;;;;;;;; ;;;; PLOT ;;;; ;;;;;;;;;;;;;; to do-plots-interest-rate ;;; Procedure to create the graph that compares the annual interest rate pattern (Euribor) set-current-plot "Interest Rate" ;;; with that of fixed interest rate. set-current-plot-pen "Euribor" plot annual-rate set-current-plot-pen "Fixed-rate" plot fixed-annual-rate end to do-plots-real-estate ;;; Procedure to create the graph that shows the variations of the real estate value during the time set-current-plot "Real Estate" ;;; and compares it with the initial value and with the minimu value choosen by the user. set-current-plot-pen "Value" plot real-estate-value set-current-plot-pen "Initial Value" plot initial-debt set-current-plot-pen "Min Value" plot min-desirable-real-estate-value end to do-plots-borrowers ;;; Procedure to create the graph that shows the composition set-current-plot "New Borrowers" ;;; of new borrowers (fixed-floating borrowers) during the time. set-current-plot-pen "Borrowers" plot n.borrowers set-current-plot-pen "Floating" plot blue-number set-current-plot-pen "Fixed" plot green-number end to do-plots-insolvents ;;; Procedure to create the graph that shows the presence of insolvent borrowers during the time. set-current-plot "Insolvent Customers" set-current-plot-pen "Insolvents" plot n.insolvents end @#$#@#$#@ GRAPHICS-WINDOW 654 10 1027 404 16 16 11.0 1 10 1 1 1 0 1 1 1 -16 16 -16 16 0 0 1 ticks CC-WINDOW 5 586 1036 681 Command Center 0 INPUTBOX 145 10 215 70 initial-debt 100000 1 0 Number SLIDER 480 10 652 43 spread spread 1.0 2.5 2.5 0.1 1 NIL HORIZONTAL MONITOR 243 72 342 117 initial-interest-rate initial-interest-rate 3 1 11 BUTTON 6 10 70 43 NIL Setup NIL 1 T OBSERVER NIL NIL NIL NIL MONITOR 137 72 241 117 NIL previous-year-rate 3 1 11 MONITOR 137 119 242 164 Euribor annual-rate 3 1 11 MONITOR 6 278 134 323 real-estate-value real-estate-value 3 1 11 INPUTBOX 218 10 288 70 initial-years 20 1 0 Number PLOT -1 324 360 447 Interest Rate NIL NIL 0.0 10.0 0.0 10.0 true true PENS "Fixed-rate" 1.0 0 -16777216 true "Euribor" 1.0 0 -5825686 true MONITOR 6 45 133 90 bank customers count turtles with [color = blue] + count turtles with [color = green] 0 1 11 CHOOSER 291 10 383 55 min-income min-income 20000 25000 30000 35000 40000 45000 50000 0 CHOOSER 386 10 478 55 max-income max-income 25000 30000 35000 40000 45000 50000 55000 60000 4 PLOT -1 449 359 572 Real Estate NIL NIL 0.0 10.0 0.0 10.0 true true PENS "Value" 1.0 0 -14835848 true "Initial Value" 1.0 0 -16777216 true "Min Value" 1.0 0 -955883 true MONITOR 6 92 134 137 floating customers (blue) count turtles with [color = blue] 3 1 11 MONITOR 6 139 133 184 fixed customers (green) count turtles with [color = green] 0 1 11 BUTTON 76 10 139 43 Go go T 1 T OBSERVER NIL NIL NIL NIL SLIDER 386 92 566 125 consumption/monthly-income consumption/monthly-income 0 1 0.5 0.1 1 NIL HORIZONTAL SLIDER 386 57 526 90 endowment/income endowment/income 0 1 0.1 0.1 1 NIL HORIZONTAL SLIDER 386 236 558 269 beta-interest/value beta-interest/value 0 2.0 1 0.1 1 NIL HORIZONTAL SLIDER 386 199 558 232 beta-interest/n.borrowers beta-interest/n.borrowers 0 2 1 0.1 1 NIL HORIZONTAL MONITOR 244 119 343 164 fixed-annual-rate fixed-annual-rate 3 1 11 MONITOR 6 185 133 230 new-borrowers n.borrowers 0 1 11 PLOT 362 325 639 447 New Borrowers NIL NIL 0.0 10.0 0.0 10.0 true true PENS "Borrowers" 1.0 1 -16777216 true "Floating" 1.0 1 -13345367 true "Fixed" 1.0 1 -10899396 true SLIDER 386 126 568 159 max-accettable-interest max-accettable-interest 4.0 10.0 8 0.5 1 NIL HORIZONTAL SWITCH 137 168 327 201 add-real-estate-value-effect? add-real-estate-value-effect? 0 1 -1000 SLIDER 385 162 628 195 min-desirable-real-estate-value min-desirable-real-estate-value 50000 120000 60000 5000 1 NIL HORIZONTAL MONITOR 6 232 133 277 insolvent-customers n.insolvents 0 1 11 SWITCH 137 237 309 270 add-n.insolvents-effect? add-n.insolvents-effect? 0 1 -1000 SLIDER 137 200 308 233 beta-value/n.borrowers beta-value/n.borrowers 0.0 2.0 1 0.1 1 NIL HORIZONTAL PLOT 363 449 640 572 Insolvent Customers NIL NIL 0.0 10.0 0.0 10.0 true false PENS "Insolvents" 1.0 1 -2674135 true @#$#@#$#@ WHAT IS IT? ----------- The model simulates the effects of changes in loan interest rates (3 mounth Euribor) on the number of mortgage loans allocated (fixed and floating interest rate), on the instalments' amount, on the borrowers' solvency and on the real estate value that constitutes the guaranty below the loan. The agents (turtles with person shape) are composed by: - persons blue: agents that rise a floating interest rate loan; - persons green: agents that rise a fixed interest rate loan; - persons white: agents blue or green that are unbankable according to their own features (monthly income, money, consumption and initial endowment); - persons red: agents that become insolvent during the simulation. The model takes inspiration from the recent facts of "sub-prime" that involved the US bank system in the last years. HOW IT WORKS ------------ Every loan required by the agent set is equal to the real estate value and the life of loan is directly proportional. The contracts' features (amount and duration) are the same for all the agents but they change during the simulation for the new borrowers according to real estate value variations. The initial number of borrowers is inversely proportional (according to the level of beta choosen from the provided slider) to the relative variation between the initial interest rate and that of a previous year (both randomly generated). This number is then proportionally divided in floating borrowers (blue) and fixed borrowers (green): if interest rates go up, the majority (70%) will rise a fixed interest rate loan, while if interest rates go down, the majority (70%) will rise a floating interest rate loan. This rule is the same during the simulation, in which the interest rate comparison is ever done between the initial interest rate and that just generated (Euribor). The Euribor is generated as follows: - with probability 1/2 the Euribor is equal to the sum of the last level generated and a random number between 0 and 0.3; - with probability 1/2 the Euribor is equal to the difference of the last level generated and a random number between 0 and 0.3. The fixed interest rate for the green agents is the first annual rate generated when they rise the contract, remaining constant until the time to maturity of the loan. Both the interest rates are transformed into monthly rates to calculate the periodic instalments that borrowers have to pay (french amortization plan, constant instalments). The features of each borrower are: monthly income, initial endowment proportional to the annual income, monthly consumption proportional to the monthly income, money available on the c/c, amount of loan, monthly instalment, capital and interest share of instalment and the relative quantities paid, residual debt, number of monthly instalment foreseen by the contract, number of instalments paid, total cost and possible amount of insolvency (difference between the loan's amount and the capital shares paid). The agents that are unbankable change their color in white, move in the centre of the monitor and then disappear. During the simulation, for every tick, the agents receive their montlhy income, pay the instalment and the consumptions. When they finish to pay their loan they disappear from the monitor. If the difference monthly income - consumption - monthly instalment is negative but the money on their c/c is congruous, they can use their liquidity as last possibility. And if also the money is not enough or it's already finished, the borrowers are insolvent. They become red and disappear from the monitor. The real estate mortgaged and then sold by the bank has a negative effect on the real estate value because the supply increases (the lost of value is equal to 100 € for each insolvent). The real estate value is naturally linked to interest rates varations. If the interest rates go up, the demand of real estate go down and consequently its value. Viceversa, if the interest rates go down the real estate value increases. The gain/lost of value is inversely proportional to the interest rate variations according to the level of beta choosen from the provided slider. Every tick, if the level of Euribor goes down the maximum accettable level choosen from the provided slider, the model creates a number of new borrowers according to interest rates variations (inversely proportional) and real estate value variations (directly proportional) and the respective betas choosen from the provided sliders. Moreover, if the real estate value go down the minimun desirable real estate value choosen from the provided slider, new agents will rise loans in despite of high levels of interest rate and this fact will increase the real estate value of 100 € each new borrower. It's possible to separate the interest rate effect from the real estate value effect on the number of new borrowers and separate the interest rate effect from the insolvents effect on the real estate value from the provided switches. HOW TO USE IT ------------- The "Setup" button creates turtles (new borrowers divided into agents blue, green and white) and generates the initial interest rate and that of a previous year (the Euribor and the fixed annual rate are equal to initial interest rate). Through the inputs "initial-debt" and "years" it's possible to choose the initial contract features. The slider "spread" allows to estabilish the spread applied by the bank. The user can also choose the range of annual income of the agent set from the chooser "min-income" and "max-income", the portion of annual income that constitutes the initial endowment for each agent from the slider "endowment/income" and the portion of monthly income that consitute the monthly consumption for each agent from the slider "consumption/monthly-income". Three monitors allow to know each time which is the number of bank's customers, the number of floating borrowers (blue) and the number of fixed borrowers (green) present in the monitor. Other two monitors indicate for each time the number of new borrowers created ("new-borrowers") and the number of insolvents ("insolvent-customers"). The sliders "beta-interest/value", "beta-interest/n.borrowers" and "beta-value/n.borrowers" allow to determine respectively the entity of real estate value variation after an interest rate variation, the entity of number variation of new borrowers after an interest rate variation and the entity of number variation of new borrowers after a real estate value variation. Through the slider "max-accettable-interest" it's possible to choose the maximum level of loan cost (not yet comprhensive of spread) that the agents can support and through the slider "min-desirable-real-estate-value" the minimum value at which the agents are disposed to purchase a real estate in despite of too high level of loan's interest rates. The switches "add-real-estate-value-effect?" and "add-n.insolvents-effect?" allow respectively to add or not the effect on the number of new borrowers created each time due to changes in the real estate value or to the collapse of real estate value under the minimum desirable real estate value and to add or not the effect on the real estate value due to a number of insolvent borrowers. There are four graphs that show some interesting relationships beetwen the pattern of interest rates, the pattern of real estate value, the entity and the composition of new borrowers during the time and the number of insolvent agents. "Interest Rate" compares the level of Euribor and the level of interest rate underwrited by those who rise a fixed interest rate loan. When the two interest go toghether it means that new borrowers are created at each time. It's very interesting to try to understand which kind of borrowers has done the best choice (ex post). "Real Estate" show the pattern of the value during the time and always compares it to the initial value and the minimum desirable value. Note that when the value go beyond the minimum desirable value (orange line) the level of Euribor is very high and, if the switch "add-real-estate-value-effect?" is on, anyway new borrowers are created. "New Borrowers" points out the number of new borrowers created each time and its composition between floating borrowers (blue) and fixed borrowers (green). "Insolvents" show the number of insolvent agents for each time. THINGS TO NOTICE ---------------- Stop the simulation in a certain point and compare the level of interest rates with the number of new borrowers and the real estate value. Are all the floating agents able to respect the loan? And if someone results insolvent, which is the entity of the insolvency and their own features? Who is able to pay all the variable instalments according to the level of income, consumption and money? Is it true that, even if probably more convenient than a fixed interest rate loan, to respect a floating loan it should be better belonging to a middle-high income's segment? It's also interesting compare the level of Euribor and the level of interest rate underwrited by those who rise a fixed interest rate loan. When the two interests go toghether, it means that new borrowers are created at each time. Try to understand which kind of borrowers has done the best choice. Then, setting the speed at level slower, try to see in the features of those agents that have discharged the debt (and so, a little before they disappear from the monitor) how much they have paid at the voice "total cost" and compare it with the size of the debt (initial real estate value) and with the actual real estate value, to quantify the possible gain-lost of the investment. THINGS TO TRY ------------- The user can modify the value of the inputs, sliders and choosers relating to: - the size of initial debt (that is equal to the initial real estate value); - the years to discarghed the loan; - the spread applied by the bank; - the range of annual income of the agent set; - th ratio initial-endowment/annual-income; - the ratio consumption/monthly-income; - the maximum level of Euribor accepted by the potential new borrowers; - the minimum real estate value desired by the potential new borrowers that can drive them to purchase in despite of too high loan's cost; - the entity of real estate value variation after an interest rate variation; - the entity of number variation of new borrowers after an interest rate variation; - the entity of number variation of new borrowers after a real estate value variation. Moreover trough the switches "add-real-estate-value-effect?" and "add-n.insolvents-effect?" it's possible respectively to add or not the effect on the number of new borrowers created each time due to changes in the real estate value or to the collapse of real estate value under the minimum desirable real estate value and to add or not the effect on the real estate value due to a number of insolvent borrowers. EXTENDING THE MODEL ------------------- We have considered as costants trough the time features like income and consumption. To improve the model we could introduce the changes in these variables due to the interest rates pattern and prices. It could simulate a simplified economy in recession or in expansion. CREDITS AND REFERENCES ---------------------- The simulation is based on : - Terna P., Boero R., Morini M., Sonnessa M. "Modelli per la complessità. La simulazione ad agenti in economia". Ed. Il Mulino 2006. http://abm.econ.unito.it/. - Ian Stewart "Langolo matematico", Le Scienza n. 313, settembre 1994. - Domenico Parisi "Mente come Cervello", Le Scienze n. 431, luglio 2004. - Pietro Terna e Riccardo Taormina "Modelli di simulazione con agenti intelligenti: il sorprendente mondo dei camaleonti". @#$#@#$#@ default true 0 Polygon -7500403 true true 150 5 40 250 150 205 260 250 airplane true 0 Polygon -7500403 true true 150 0 135 15 120 60 120 105 15 165 15 195 120 180 135 240 105 270 120 285 150 270 180 285 210 270 165 240 180 180 285 195 285 165 180 105 180 60 165 15 arrow true 0 Polygon -7500403 true true 150 0 0 150 105 150 105 293 195 293 195 150 300 150 box false 0 Polygon -7500403 true true 150 285 285 225 285 75 150 135 Polygon -7500403 true true 150 135 15 75 150 15 285 75 Polygon -7500403 true true 15 75 15 225 150 285 150 135 Line -16777216 false 150 285 150 135 Line -16777216 false 150 135 15 75 Line -16777216 false 150 135 285 75 bug true 0 Circle -7500403 true true 96 182 108 Circle -7500403 true true 110 127 80 Circle -7500403 true true 110 75 80 Line -7500403 true 150 100 80 30 Line -7500403 true 150 100 220 30 butterfly true 0 Polygon -7500403 true true 150 165 209 199 225 225 225 255 195 270 165 255 150 240 Polygon -7500403 true true 150 165 89 198 75 225 75 255 105 270 135 255 150 240 Polygon -7500403 true true 139 148 100 105 55 90 25 90 10 105 10 135 25 180 40 195 85 194 139 163 Polygon -7500403 true true 162 150 200 105 245 90 275 90 290 105 290 135 275 180 260 195 215 195 162 165 Polygon -16777216 true false 150 255 135 225 120 150 135 120 150 105 165 120 180 150 165 225 Circle -16777216 true false 135 90 30 Line -16777216 false 150 105 195 60 Line -16777216 false 150 105 105 60 car false 0 Polygon -7500403 true true 300 180 279 164 261 144 240 135 226 132 213 106 203 84 185 63 159 50 135 50 75 60 0 150 0 165 0 225 300 225 300 180 Circle -16777216 true false 180 180 90 Circle -16777216 true false 30 180 90 Polygon -16777216 true false 162 80 132 78 134 135 209 135 194 105 189 96 180 89 Circle -7500403 true true 47 195 58 Circle -7500403 true true 195 195 58 circle false 0 Circle -7500403 true true 0 0 300 circle 2 false 0 Circle -7500403 true true 0 0 300 Circle -16777216 true false 30 30 240 cow false 0 Polygon -7500403 true true 200 193 197 249 179 249 177 196 166 187 140 189 93 191 78 179 72 211 49 209 48 181 37 149 25 120 25 89 45 72 103 84 179 75 198 76 252 64 272 81 293 103 285 121 255 121 242 118 224 167 Polygon -7500403 true true 73 210 86 251 62 249 48 208 Polygon -7500403 true true 25 114 16 195 9 204 23 213 25 200 39 123 cylinder false 0 Circle -7500403 true true 0 0 300 dot false 0 Circle -7500403 true true 90 90 120 face happy false 0 Circle -7500403 true true 8 8 285 Circle -16777216 true false 60 75 60 Circle -16777216 true false 180 75 60 Polygon -16777216 true false 150 255 90 239 62 213 47 191 67 179 90 203 109 218 150 225 192 218 210 203 227 181 251 194 236 217 212 240 face neutral false 0 Circle -7500403 true true 8 7 285 Circle -16777216 true false 60 75 60 Circle -16777216 true false 180 75 60 Rectangle -16777216 true false 60 195 240 225 face sad false 0 Circle -7500403 true true 8 8 285 Circle -16777216 true false 60 75 60 Circle -16777216 true false 180 75 60 Polygon -16777216 true false 150 168 90 184 62 210 47 232 67 244 90 220 109 205 150 198 192 205 210 220 227 242 251 229 236 206 212 183 fish false 0 Polygon -1 true false 44 131 21 87 15 86 0 120 15 150 0 180 13 214 20 212 45 166 Polygon -1 true false 135 195 119 235 95 218 76 210 46 204 60 165 Polygon -1 true false 75 45 83 77 71 103 86 114 166 78 135 60 Polygon -7500403 true true 30 136 151 77 226 81 280 119 292 146 292 160 287 170 270 195 195 210 151 212 30 166 Circle -16777216 true false 215 106 30 flag false 0 Rectangle -7500403 true true 60 15 75 300 Polygon -7500403 true true 90 150 270 90 90 30 Line -7500403 true 75 135 90 135 Line -7500403 true 75 45 90 45 flower false 0 Polygon -10899396 true false 135 120 165 165 180 210 180 240 150 300 165 300 195 240 195 195 165 135 Circle -7500403 true true 85 132 38 Circle -7500403 true true 130 147 38 Circle -7500403 true true 192 85 38 Circle -7500403 true true 85 40 38 Circle -7500403 true true 177 40 38 Circle -7500403 true true 177 132 38 Circle -7500403 true true 70 85 38 Circle -7500403 true true 130 25 38 Circle -7500403 true true 96 51 108 Circle -16777216 true false 113 68 74 Polygon -10899396 true false 189 233 219 188 249 173 279 188 234 218 Polygon -10899396 true false 180 255 150 210 105 210 75 240 135 240 house false 0 Rectangle -7500403 true true 45 120 255 285 Rectangle -16777216 true false 120 210 180 285 Polygon -7500403 true true 15 120 150 15 285 120 Line -16777216 false 30 120 270 120 leaf false 0 Polygon -7500403 true true 150 210 135 195 120 210 60 210 30 195 60 180 60 165 15 135 30 120 15 105 40 104 45 90 60 90 90 105 105 120 120 120 105 60 120 60 135 30 150 15 165 30 180 60 195 60 180 120 195 120 210 105 240 90 255 90 263 104 285 105 270 120 285 135 240 165 240 180 270 195 240 210 180 210 165 195 Polygon -7500403 true true 135 195 135 240 120 255 105 255 105 285 135 285 165 240 165 195 line true 0 Line -7500403 true 150 0 150 300 line half true 0 Line -7500403 true 150 0 150 150 pentagon false 0 Polygon -7500403 true true 150 15 15 120 60 285 240 285 285 120 person false 0 Circle -7500403 true true 110 5 80 Polygon -7500403 true true 105 90 120 195 90 285 105 300 135 300 150 225 165 300 195 300 210 285 180 195 195 90 Rectangle -7500403 true true 127 79 172 94 Polygon -7500403 true true 195 90 240 150 225 180 165 105 Polygon -7500403 true true 105 90 60 150 75 180 135 105 plant false 0 Rectangle -7500403 true true 135 90 165 300 Polygon -7500403 true true 135 255 90 210 45 195 75 255 135 285 Polygon -7500403 true true 165 255 210 210 255 195 225 255 165 285 Polygon -7500403 true true 135 180 90 135 45 120 75 180 135 210 Polygon -7500403 true true 165 180 165 210 225 180 255 120 210 135 Polygon -7500403 true true 135 105 90 60 45 45 75 105 135 135 Polygon -7500403 true true 165 105 165 135 225 105 255 45 210 60 Polygon -7500403 true true 135 90 120 45 150 15 180 45 165 90 square false 0 Rectangle -7500403 true true 30 30 270 270 square 2 false 0 Rectangle -7500403 true true 30 30 270 270 Rectangle -16777216 true false 60 60 240 240 star false 0 Polygon -7500403 true true 151 1 185 108 298 108 207 175 242 282 151 216 59 282 94 175 3 108 116 108 target false 0 Circle -7500403 true true 0 0 300 Circle -16777216 true false 30 30 240 Circle -7500403 true true 60 60 180 Circle -16777216 true false 90 90 120 Circle -7500403 true true 120 120 60 tree false 0 Circle -7500403 true true 118 3 94 Rectangle -6459832 true false 120 195 180 300 Circle -7500403 true true 65 21 108 Circle -7500403 true true 116 41 127 Circle -7500403 true true 45 90 120 Circle -7500403 true true 104 74 152 triangle false 0 Polygon -7500403 true true 150 30 15 255 285 255 triangle 2 false 0 Polygon -7500403 true true 150 30 15 255 285 255 Polygon -16777216 true false 151 99 225 223 75 224 truck false 0 Rectangle -7500403 true true 4 45 195 187 Polygon -7500403 true true 296 193 296 150 259 134 244 104 208 104 207 194 Rectangle -1 true false 195 60 195 105 Polygon -16777216 true false 238 112 252 141 219 141 218 112 Circle -16777216 true false 234 174 42 Rectangle -7500403 true true 181 185 214 194 Circle -16777216 true false 144 174 42 Circle -16777216 true false 24 174 42 Circle -7500403 false true 24 174 42 Circle -7500403 false true 144 174 42 Circle -7500403 false true 234 174 42 turtle true 0 Polygon -10899396 true false 215 204 240 233 246 254 228 266 215 252 193 210 Polygon -10899396 true false 195 90 225 75 245 75 260 89 269 108 261 124 240 105 225 105 210 105 Polygon -10899396 true false 105 90 75 75 55 75 40 89 31 108 39 124 60 105 75 105 90 105 Polygon -10899396 true false 132 85 134 64 107 51 108 17 150 2 192 18 192 52 169 65 172 87 Polygon -10899396 true false 85 204 60 233 54 254 72 266 85 252 107 210 Polygon -7500403 true true 119 75 179 75 209 101 224 135 220 225 175 261 128 261 81 224 74 135 88 99 wheel false 0 Circle -7500403 true true 3 3 294 Circle -16777216 true false 30 30 240 Line -7500403 true 150 285 150 15 Line -7500403 true 15 150 285 150 Circle -7500403 true true 120 120 60 Line -7500403 true 216 40 79 269 Line -7500403 true 40 84 269 221 Line -7500403 true 40 216 269 79 Line -7500403 true 84 40 221 269 x false 0 Polygon -7500403 true true 270 75 225 30 30 225 75 270 Polygon -7500403 true true 30 75 75 30 270 225 225 270 @#$#@#$#@ NetLogo 4.0.2 @#$#@#$#@ @#$#@#$#@ @#$#@#$#@ @#$#@#$#@ @#$#@#$#@ default 0.0 -0.2 0 0.0 1.0 0.0 1 1.0 0.0 0.2 0 0.0 1.0 link direction true 0 Line -7500403 true 150 150 90 180 Line -7500403 true 150 150 210 180 @#$#@#$#@