(1) The right-hand side of the equation represents the probability that the random change in sorghum prices takes on a value less than or equal to x. As the change in rain is a continuous variable, its probability density function is defined as follows: (2) This graphical representation has been preferred to the probability density function due to the problems associated to its use (see Hardaker 2004). et al. 3. The parametric model The log-log model tested makes reference to the following conceptual framework based on the literature, the seasonal calendar and interviews with Sudanese farmers. The level of sorghum marketable surplus represents the main determinant of its price. It is function of the domestic production, particularly of households in rural areas (El-Dukheri 2007). For this reason, the first aspect taken into consideration is the annual change of the monthly production of sorghum (Q) specified as follows: (3) where is the natural logarithm, is the market (Obeid or Kordofan), is the year, is the month, ln j t m with data starting from January, and . is rainfall and is defined taken into consideration the seasonal R calendar illustrated in Figure 1. Figure 1 Seasonal calendar for sorghum Rain-fed and irrigated – – Dry season Hunger season (Mar-Apr) (May-Aug) Rainy season Major market Sowing and re-sowing Major market supply (Nov-Apr) supply (Jun-Aug) First and second Land preparation and planting weeding Harvesting (Oct-Dec) (Apr-Jun) (Aug-Sep) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
(1) The right-hand side of the equation represents the probability that the random change in sorghum prices takes on a value less than or equal to x. As the change in rain is a continuous variable, its probability density function is defined as follows: (2) This graphical representation has been preferred to the probability density function due to the problems associated to its use (see Hardaker et al. 2004). 3. The parametric model The log-log model tested makes reference to the following conceptual framework based on the literature, the seasonal calendar and interviews with Sudanese farmers. The level of sorghum marketable surplus represents the main determinant of its price. It is function of the domestic production, particularly of households in rural areas (El-Dukheri 2007). For this reason, the first aspect taken into consideration is the annual change of the monthly production of sorghum (Q) specified as follows: (3) where ln is the natural logarithm, j is the market (Obeid or Kordofan), t is the year, m is the month, with data starting from January, and . R is rainfall and is defined taken into consideration the seasonal calendar illustrated in Figure 1. Figure 1 – Seasonal calendar for sorghum – Rain-fed and irrigated Dry season (Mar-Apr) Hunger season (May-Aug) Rainy season Major market supply (Nov-Apr) Sowing and re-sowing (Jun-Aug) Major market supply Land preparation and planting (Apr-Jun) First and second weeding (Aug-Sep) Harvesting (Oct-Dec) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
aafinalesorghum.docx