globals [cycle_# bank_from bank_to amount] breed [banks bank] breed [central] banks-own [balance central_treasury maximum_limit] central-own [treasury] ;-------------------- to setup clear-all set-default-shape banks "banks" setup-banks set-default-shape central "central" setup-central set cycle_# 0 end ;-------------------- to setup-central create-central 1 ask central [ set color 74 set size 3 fd 0 set treasury (Maximum_amount_of_loans_granted_as_the_central_bank) ] end ;------------------------ to setup-banks create-ordered-banks 10 ask banks [ set color 94 set size 3 fd 10 set balance 0 set central_treasury 0 ; is the amount of loans granted of central bank to the bank set maximum_limit ( - Maximum_amount_of_loans_granted_as_the_central_bank) ] end ;------------------------ to go file-open "payments.txt" while [not file-at-end?] [ set bank_from file-read set bank_to file-read set amount file-read ask bank bank_from [ set balance (balance - amount) ; where (sum [central_tresury] of banks is the total of money lent from the central bank to the other banks ; three conditions are set that must have respected ; first condition points out the number that identifies the bank that is necessary to consider ; second condition points out under which budget the suitable bank in the first condition asks for the loan ; third condition points out that the central bank doesn't grant a general amount of loans superior to the amount points out in the slider if ( ( who = 0 ) and ( balance <= 0) and (sum [central_treasury] of banks >= maximum_limit ) )[set balance (balance + 50000)] if ( ( who = 1 ) and ( balance <= 5000) and (sum [central_treasury] of banks >= maximum_limit ) )[set balance (balance + 45000)] if ( ( who = 2 ) and ( balance <= -5000) and (sum [central_treasury] of banks >= maximum_limit ) )[set balance (balance + 55000)] if ( ( who = 3 ) and ( balance <= 10000) and (sum [central_treasury] of banks >= maximum_limit ) )[set balance (balance + 40000)] if ( ( who = 4 ) and ( balance <= -10000) and (sum [central_treasury] of banks >= maximum_limit ) )[set balance (balance + 60000)] if ( ( who = 5 ) and ( balance <= -15000) and (sum [central_treasury] of banks >= maximum_limit ) )[set balance (balance + 65000)] if ( ( who = 6 ) and ( balance <= 15000) and (sum [central_treasury] of banks >= maximum_limit ) )[set balance (balance + 35000)] if ( ( who = 7 ) and ( balance <= -20000) and (sum [central_treasury] of banks >= maximum_limit ) )[set balance (balance + 70000)] if ( ( who = 8 ) and ( balance <= -25000) and (sum [central_treasury] of banks >= maximum_limit ) )[set balance (balance + 75000)] if ( ( who = 9 ) and ( balance <= -30000) and (sum [central_treasury] of banks >= maximum_limit ) )[set balance (balance + 80000)] ; in this way the banks can only ask money to the central bank when the total of the loans that the central has granted to the banks of the system are smaller ; that the amount points aout in the slider if ( ( who = 0 ) and ( balance <= 0) and (sum [central_treasury] of banks >= maximum_limit) )[set central_treasury (central_treasury - 50000)] if ( ( who = 1 ) and ( balance <= 5000) and (sum [central_treasury] of banks >= maximum_limit) )[set central_treasury (central_treasury - 45000)] if ( ( who = 2 ) and ( balance <= -5000) and (sum [central_treasury] of banks >= maximum_limit) )[set central_treasury (central_treasury - 55000)] if ( ( who = 3 ) and ( balance <= 10000) and (sum [central_treasury] of banks >= maximum_limit) )[set central_treasury (central_treasury - 40000)] if ( ( who = 4 ) and ( balance <= -10000) and (sum [central_treasury] of banks >= maximum_limit) )[set central_treasury (central_treasury - 60000)] if ( ( who = 5 ) and ( balance <= -15000) and (sum [central_treasury] of banks >= maximum_limit) )[set central_treasury (central_treasury - 65000)] if ( ( who = 6 ) and ( balance <= 15000) and (sum [central_treasury] of banks >= maximum_limit) )[set central_treasury (central_treasury - 35000)] if ( ( who = 7 ) and ( balance <= -20000) and (sum [central_treasury] of banks >= maximum_limit) )[set central_treasury (central_treasury - 70000)] if ( ( who = 8 ) and ( balance <= -25000) and (sum [central_treasury] of banks >= maximum_limit) )[set central_treasury (central_treasury - 75000)] if ( ( who = 9 ) and ( balance <= -30000) and (sum [central_treasury] of banks >= maximum_limit) )[set central_treasury (central_treasury - 80000)] ; in this way the central banks grants loans until to a maximum limit and after it fails if (balance <= 0) [set color red] if (balance > 0) [set color 94] ifelse show-balance? [ set label balance ] [ set label "" ] ] ask bank bank_to [ set balance (balance + amount) if (balance <= 0) [set color red] if (balance > 0) [set color 94] ifelse show-balance? [ set label balance ] [ set label "" ] ] ask central[ ; in this way the central banks grants loans until to a maximum limit points out in the slider and after it fails set treasury (treasury + ( sum [central_treasury] of banks)) if (treasury <= 0) [ die ] ifelse show-treasury? [ set label treasury ] [ set label "" ] ] do-plots set cycle_# cycle_# + 1 wait 0.3 ] file-close end ;-------------------------- to do-plots set-current-plot "Number of banks" set-current-plot-pen "Banks in deficit" plot count banks with [color = red] set-current-plot "Number of banks" set-current-plot-pen "Banks in credit" plot count banks with [color = 94] set-current-plot "Amounts" set-current-plot-pen "Deficit" plot sum [balance] of banks with [balance <= 0] set-current-plot "Amounts" set-current-plot-pen "Cash Balances" plot sum [balance] of banks with [balance > 0] set-current-plot "Amounts" set-current-plot-pen "Central Bank" plot sum [treasury] of central end ; ------------------------- @#$#@#$#@ GRAPHICS-WINDOW 264 5 530 270 11 10 11.143 1 10 1 1 1 0 1 1 1 -11 11 -10 10 0 0 1 ticks CC-WINDOW 5 586 539 681 Command Center 0 MONITOR 479 272 529 313 NIL cycle_# 0 1 10 BUTTON 128 10 238 43 go go NIL 1 T OBSERVER NIL NIL NIL NIL BUTTON 7 10 114 43 setup setup NIL 1 T OBSERVER NIL NIL NIL NIL SWITCH 7 48 238 81 show-balance? show-balance? 0 1 -1000 PLOT 11 312 529 432 Number of banks time number 0.0 10.0 0.0 10.0 true true PENS "Banks in deficit" 1.0 0 -2674135 true "Banks in credit" 1.0 0 -13345367 true MONITOR 8 125 236 170 Total number of banks count banks 17 1 11 SWITCH 8 87 236 120 show-treasury? show-treasury? 0 1 -1000 MONITOR 10 176 237 221 Number of banks in deficit count banks with [color = red] 17 1 11 MONITOR 11 226 237 271 Number of banks in credit count banks with [color = 94] 17 1 11 PLOT 11 437 527 572 Amounts time import 0.0 10.0 0.0 10.0 true true PENS "Deficit" 1.0 0 -2674135 true "Cash Balances" 1.0 0 -13345367 true "Central Bank" 1.0 0 -10899396 true SLIDER 11 275 422 308 Maximum_amount_of_loans_granted_as_the_central_bank Maximum_amount_of_loans_granted_as_the_central_bank 0 9000000 0 1000 1 NIL HORIZONTAL @#$#@#$#@ WHAT IS IT? ----------- The model simulates the payments among the banks that are operating in a given economic system. In this project there are 10 banks that effect the exchange of money between them and a central bank intervening in specific cases. HOW IT WORKS ------------ The banks follow a set of simple rules. The banks effect exchanges of money among themselves, and the amount of every single operation is read in a file. When the budget of a bank is under a certain level (for every bank it is different, and can be positive or negative) then the bank asks the central bank for a loan. The loans are not granted in a boundless way, in fact the central bank has a limited quantity of money that it can introduce in to the system (a slider controls this). HOW TO USE IT ------------- Click the SETUP button to set up the banks (blue) and the central bank (green). Click the GO button to start the simulation. A bank turns red when it's budget is under zero and a the central bank fails when it grants loans over the limit of the slider. There is one slider. MAXIMUM_AMOUNT_OF_LOANS_GRANTED_AS_THE_CENTRAL_BANK control the limit of loans that the central bank can grant. Changes in this slider do not take effect until the next setup. While the simulation runs, two plots are displayed. In the plot NUMBER OF BANKS the number of banks in deficit and the number of banks with cash balance are displayed. In the plot AMOUNTS the amounts of deficit, the amount of cash balance and the money of the central bank are displayed. THINGS TO NOTICE ---------------- Watch the TOTAL NUMBER OF BANKS monitor, the NUMBER OF BANKS IN DEFICIT monitor, the NUMBER OF BANKS IN CREDIT monitor and the NUMBER OF BANKS plot to see how the number of banks changes over time. You can see that the total the number of the banks doesn't change, but the number of banks in deficit and the number of banks with a cash balance change over time. The simulation will stop when the file finishes. The number of banks in deficit and the number of banks with a cash balance oscillates and this is determined by the operations that the banks effect. In particular you can observe that when the number of banks in deficit increases, the number of banks with a cash balance decrease and the sum corresponds to the number that you can see in the TOTAL NUMBER OF BANKS monitor. THINGS TO TRY ------------- Increasing the amount of money that the central bank can grant as loans, to the point at which (any/all) banks of the system (is/are) in deficit be reached? Start with a MAXIMUM_AMOUNT_OF_LOANS_GRANTED_AS_THE_CENTRAL_BANK of zero, let the file be read and after, you can see the situation. Particularly you can see the number of banks in deficit, the number of banks in cash balance, the amount of liquidity in the system and the amount of deficit of the banks. The project can do experiments with different amounts of loans granted as the central bank. It can be seen that, if you increases the quantity of money that the central bank introduces into the system, it will also increase the number of the banks with a cash balance, while it will be decreasing the number of the banks in deficit. This will also increase the general liquidity of the system. The project can do experiments for every amount that can be selected in the slider. EXTENDING THE MODEL ------------------- The model has necessarily simplified its subject area substantially, and assumes the central bank does not refuse any loans. The model therefore provides numerous opportunities for extension: In the model all the operations among the banks are made in the order in which they are written in the file, in this way the banks make payments even if they are in deficit. The model could be changed to reflect a more realistic view where the banks could make the payments only if they have the necessary money to do it. Money could arrive at the bank, that has to make the payment through loans, reimbursed from the central bank or reimbursed from other banks in the system that have a cash balance. Extending the model by adding this would make it more realistic. The model also assumes that there aren't any costs. Even if the banks have to take on loan money they don't to pay any interest. The model could be changed to reflect a more realistic view. When a bank takes on a loan it should pay interest that changes according to the time it holds the money without returning it. If you add the condition that says that a bank can make payments only when it has the available cash and the banks have to pay interest to the central bank, with the interest changing according to the time for which the bank delays the payment. 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