To get informed about the expected income in the new market, the farmer has the chance to collect the technical- and management efficiency factors of one farmer whom already produces for that market every time-step. In the model this looks as follows: every month, all farmers interact with one random farmer in their network , all farmers check whether they want to convert from conventional to organic, or from organic to conventional , if farmers want to convert, they collect information from one random farmer producing for the desired market and during a news interaction, one farmer influences 75% of conventional farmers and one farmer influences 75% of organic farmers. These farmers are determined independently and there is a chance that they are in fact the same farmer. A model parameter defines the probability that the selected farmer belongs to the other market than the influenced farmers. Each of these selected farmers for ‘news interaction’ are randomly picked from the applicable farmer population. Farmers in the news interaction update their attitude according to the interaction mechanism described below. Note that this interaction is one-time only, and does not imply a new permanent link. Every year, at the end of the year, the age of the farmers is updated. Then farmers check whether they retire and whether they have a successor. They update their income and their statuses . If they want to switch to another market, they check whether it is profitable to convert at this moment and if so, they convert and update their variables accordingly. Model outputs were derived after 180 months, i.e. time steps, corresponding to 15 years, which represent the time from January 2000 to December 2015. The remainder of this section outlines the interaction mechanism used for both network interaction and news interaction, the retirement and succession mechanism,vertical grow rack income calculation, and market price dynamics .

The topic for interaction is randomly chosen per interaction. When farmer A interacts with farmer B, the effect of the interaction on farmer A depends on the credibility of farmer B to farmer A. The perceived credibility of farmer B depends on a number of factors: the innovativeness of farmer A, the farming styles of farmer A and farmer B, the status farmer A assigns to farmer B according to farmer A’s farming style , the farm sizes of farmer A and farmer B, and the markets of farmer A and farmer B. Following the Social Identity Approach, the status of farmer B, as well as the similarity in farming style farm size and market between the two farmers, matter for the perceived credibility of farmer B. The basic idea is that an innovative farmer A considers the status of farmer B more than the similarity between them, while a conservative farmer A considers the similarity between them more than the status of farmer B. This results in the formula given in Eq. below. For the calculation of the status value and the similarity value see Eqs. and respectively. Each farmer has three statuses: idealist-status, craftsmen-status, and entrepreneur-status . The idealist status is based on the market the farmer produces for and changes when the farmer converts. The craftsman status is based on productivity performance and changes with farm succession through re-initialisation of productivity performance.Income performance changes with market conversion through changes in farm size and market price, and with farm succession through re-initialisation of productivity and management performance value. Farm size changes with conversion: fewer pigs can be kept on the same m2 in organic farming. The total area of the building is static throughout the model run. Succession is the only procedure through which ‘new’ farmers enter the model and through which change in farming style is possible. Each farmer annually checks whether s/he has the age to retire . If s/he retires, there might be a successor. This depends on a random factor for 50%, and on the farmer’s average income over the past five years for the remaining 50%. The lower the average income compared to the modal income of all farmers, the smaller the chance to have a successor.

This formula indicates that if the income is modal, the chance is 50%, while if the income is higher or lower the chance decreases relatively steep. If there is a successor, the model sets his/her age, innovativeness, management and productivity performance, and network according to the corresponding initialisation parameters . The farming style of the successor is determined by a predefined chance that the successor has the same farming style as his predecessor. If it is not the same, the farming style is randomly selected. At last, the market attitudes are re-initialised. This is for 90% derived from the attitude of his best friend and for 10% randomly. The best friend is a connected farmer who is most similar to him in terms of farming style and age, and only influences the successor at his/her initialisation. Two categories of outputs were selected to analyse the effect of parameter changes on model outputs: the size of the organic market, i.e. the number of organic farmers and organic pigs; and the shares of farming styles in the organic market, i.e. the number of idealists, craftsmen and entrepreneurs in the organic market. First, an exploratory analysis on the effects of the social influence parameters on model outputs was done, because their initialization values are uncertain. The social influence parameters were: the credibility thresholds: the level of credibility another farmer needs to have before it leads to social influence; the weights of the factors that determine similarity: the weight of farm size, market and farming style were each set to zero in turn; and the magnitude of influence once the credibility of the farmer exceeds the threshold . We explored the effect of three categories of social influence parameters on all selected outputs: two credibility threshold parameters ; three similarity parameters ; and four different values for the ‘magnitude of influence’ parameter when influence takes place . The two credibility threshold parameters have most influence on the size of the organic market, then comes the similarity parameter ‘weight farming style’ and ‘weight farm size’. The credibility threshold parameters also affect the diversity of farming styles in the organic market: the number of organic farmers with a craftsmen and entrepreneurial farming style increases when the credibility thresholds are closer to zero . The ‘weight farming style’ also affects the diversity of farming styles in the organic market: when similarity in farming style does not affect whether or not influence takes place , diversity of organic farmers’ farming styles also increases. The magnitude of influence and ‘weight market’ have hardly any effect on model outputs . Overall, the results show that the five most influential parameters on the number of organic farmers and pigs are : trend in demand, which affects the organic meat price in our model ; the social influence parameter, which determines the magnitude of influence that follows from interaction ; the parameter that determines the minimum value a farmers’ attitude needs to have for a farmer to start calculating the economic benefits of conversion ; the parameter that determines the farming style of the successor ; and ‘the elasticity of demand for organic meat’, which also influences the price of organic meat. In addition, the results show that four out of eight parameters have a consistent influence on the size of the organic market over all three scenarios listed from highest to lowest influence : an increase in demand increases the number of organic farmers and organic pigs; an increase in the threshold for a farmers’ attitude to start calculating the economic benefits of conversion decreases the number of organic farmers and organic pigs; an increase in the likelihood of influence between farmers leads to more organic farmers and organic pigs ; and an increase in the probability that the successor has the same farming style as his/ her predecessor leads to a decrease in the number of organic farmers and organic pigs .

The remaining parameters differ in their effects on the size of the organic market across the scenarios. In the scenario with a higher likelihood of influence , a decrease in the magnitude of influence that follows from interaction leads to more organic farmers and organic pigs, vertical grow table while in the scenario with a lower likelihood of influence that same decrease leads to less organic farmers and organic pigs. This seems to indicate that when interaction less frequently leads to influence, the influence that takes place is more often positive. The same trend is the case for the negative social influence parameter : in the scenario with a higher likelihood of influence , a decrease in the likelihood of negative social influence leads to more organic farmers and organic pigs, while in the scenario with a lower likelihood of influence, that same decrease leads to less organic farmers and organic pigs. This seems to indicate that when interaction less frequently leads to influence, negative social influence stimulates conversion. In the baseline scenario stronger influence from successors’ peers leads to less organic farmers and organic pigs, while in the high and low threshold scenarios this leads to more organic farmers and organic pigs. The same effect can be found on the number of organic idealists , meaning that this effect can be attributed to idealists, who have a more positive attitude towards organic when there is either a higher likelihood of influence in interaction or a lower likelihood of influence in interaction . Finally, an increase in the price elasticity of demand for organic meat leads to more organic pigs in the low threshold scenario, produced by fewer organic farmers. In the other scenarios, a lower price elasticity leads to fewer organic farmers and organic pigs. This effect suggests that a lower price elasticity favours farmers with a large farm size in the low threshold scenario . This scenario also results in more organic craftsmen .

Overall, the results show that the five most influential parameters on the organic farmers’ farming styles are : the price elasticity of demand for organic meat, which affects the number of organic craftsmen and organic entrepreneurs most; the magnitude of influence when influence takes place; the threshold for a farmers’ attitude to start calculating the economic benefits of conversion ; the probability the successor has the same farming style as his predecessor; and the parameter that determines the fraction on which the successor’s attitude is based on peers instead of a random value for attitude.There is only one parameter that has a consistent effect on all three outputs over all three scenarios. This is the trend in demand: a higher trend in demand leads to more organic idealists, organic craftsmen and organic entrepreneurs. For the number of organic idealists there are five consistent parameters: a lower price elasticity of demand for organic meat results in more organic idealists, irrelevant of the likelihood of influence; a higher threshold for attitude leads to less organic idealists; a higher probability that the successor has the same farming style as his predecessor leads to less organic idealists; an increase in the percentage of farmers who receive news leads to more organic idealists; and when similarity in farming style is more important for the credibility of another farmer , the number of idealists increase. Two parameters are consistent in their effect on the number of organic craftsmen and organic entrepreneurs: an increase in the fraction on which the successor bases his attitude on peers leads to less organic craftsmen and entrepreneurs; and an increase in the threshold of credibility also leads to less organic craftsmen and organic entrepreneurs. Two parameters have a different effect on the number of organic idealists, organic craftsmen and organic entrepreneurs across scenarios: an increase in the magnitude of influence when influence takes place leads to less organic idealists in the low threshold scenario and baseline scenario, while it leads to an increase in organic craftsmen and organic entrepreneurs in these scenarios.