SWAP (Statewide Agricultural Production Model)
General Description | The Statewide Agricultural Production Model (SWAP) is a multi-region, multi-input and output model of agricultural production, which self-calibrates using the method of Positive Mathematical Programming (PMP). PMP simulates the effects of policy changes on cropping patterns at the extensive and intensive margins by integrating observed data into model calibration. The model chooses the optimal amounts of land, water, labor, and other input use subject to these constraints and definitions. Profit is revenue minus costs, where revenue is price x yield per acre times total acres. The model website is at: http://swap.ucdavis.edu |
Model Domain | Agricultural economics of California |
Developer | Howitt, Medellin-Azuara, MacEwan, and Lund. Originally at the University of California at Davis (UC Davis) |
Hardware computing requirements | Not specified |
Code language | GAMS |
Original application | Developed as an agricultural economic component of CALVIN model of California water systems. http://calvin.ucdavis.edu |
Public/proprietary and cost | For research-related applications available through UC Davis Center for Watershed Sciences or UC Merced (public). Business application through ERA Economics (proprietary). |
Physically or empirically based | Empirical |
Mathematical methods used | Based on Positive Mathematical Programming (Howitt 1995) calibrated to a base datasets on crop production input use, prices, costs and yields. Constant Elasticity of Substitution (CES) production functions are generated for every crop in every region. |
Input data requirements | Input data requirements include (brackets include values in parentheses refer to example datasets):
|
Outputs | Outputs for 27 base regions (21 CVPM regions) in the Central Valley for 20 crop groups.
|
Pre-processing and post-processing tools | None specified. |
Representation of uncertainty | None specified. |
Prevalence | Used in policy analysis by both academic and state agencies. |
Ease of use for public entities | Requires knowledge of GAMS software and access to program through UC Davis. Alternatively, ERA Economics provides paid access to model interface and modelling services for SWAP. |
Ease of obtaining information and availability of technical support | Through Mode can be obtained through UC Davis Center for Watershed Sciences for research purposes. ERA Economics provides services to run scenarios. Freely available manuals or information on technical model runs is not currently available. |
Source code availability | Not freely available. |
Status of model development | Model Version 6.1 is available for research and other application through UC Davis Center for Watershed Sciences. Version RTS (decreasing returns to scale) available through ERA economics. |
Challenges for integration | Currently integrated with CALVIN, IMPLAN, and CALSIM II models. Detailed inputs. Constrained crop groups may not map well to other models. New crop groups or updated crop valuation requires calibration for economics as well as land use. Model is data driven, can be run without recoding by changing input data. Model output scale may not match with other models. |
...