Below is a model of construction in the real estate industry. A long delay exists between the need to close the gap in houses and the completing of construction of those houses. This model features a negative feedback loop with several delays.
houses.mdl Equations
average house life = 1200
Units: Month
building = Planned Houses / time to plan to build
Units: house/Month
completing = Houses In Construction / time to build houses
Units: house/Month
demolishing = Houses Completed / average house life
Units: house/Month
gap in houses = number of houses required - Houses Completed
Units: house
Houses Completed = INTEG( completing - demolishing , 5000)
Units: house
| Houses In Construction = INTEG( building - completing , |
| building * time to build houses ) |
Units: house
| Planned Houses = INTEG( planning - building , |
| planning * time to plan to build ) |
Units: house
| planning = MAX ( 0, replacement houses + ( gap in houses / |
| time to respond to gap ) ) |
Units: house/Month
replacement houses = demolishing
Units: house/Month
time to build houses = 6
Units: Month
time to plan to build = 3
Units: Month
time to respond to gap = 8
Units: Month
