Journal on Policy and Complex Systems
2 . Balance supply and demand : Following this policy , when a producer attempts to join the food hub , the manager will assess total system supply and demand levels from the previous distribution cycle for the candidate producer ’ s product type . If the supply of that food type in the previous cycle is less than 120 % of the demand ( allowing for future growth ), then the manager will allow the producer to join ; otherwise , the producer is removed from the system .
3 . Account for producer size : The manager evaluates a producer in terms of system supply and demand ( as in Policy 2 ) but makes exceptions for small-sized producers . That is , if a small dairy producer requests membership , even if the food hub ’ s supply of dairy items from other producers is already much greater than existing demand , the manager will make an exception to the policy and will allow that producer to join . This policy reflects the food hub ’ s socially responsible imperative to support small-scale regional producers .
4 . Account for producer price level : This policy is similar to Policy 3 , but here the manager will make an exception for producers who are at a low price level ; that is , such producers will be allowed to join even if the supply – demand ratio of their food type is greater than 120 %. This policy does not reflect current practices at the Iowa food hub but serves as a “ what-if ” scenario to determine what would happen to the system if the food hub decided to place a greater emphasis on improving access for low-income consumers .
5 . Account for producer size and price : This policy combines Policies 2 , 3 , and 4 , such that the manager ’ s selection policy is very generous — producer membership is only restricted if the candidate producer is medium / large size and / or medium / high price , and the supply for that producer ’ s product type is greater than 120 % of demand .
The model was run for 1000 replications for each of the five policies . The length of each model run was 110 time steps ( i . e ., distribution cycles ), which represents five years of system operation at 22 distribution cycles per year . The food hub manager has two primary objectives : maximizing food hub revenues while providing support and economic opportunities for regional producers . To reflect this , the following output metrics were captured at the end of each replication :
• Total volume of food units traded through the food hub
• Total number of consumer and producer agents participating
• Average “ age ” ( i . e ., length of participation ) of participating producer and consumer agents
• Number of small- , medium- , and large-sized participating producer agents
• Number of low- , medium- , and high-priced participating producer agents
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