1. School of Agricultural Sciences, University of Mpumalanga, Cnr R40 and D725 Roads, Mbombela 1200, South Africa
2. College of Agriculture and Environmental Sciences, University of South Africa, Private Bag X7, Florida Campus, Johannesburg 1709, South Africa
3. Agricultural Research Council-Central Office, Economic Analysis Unit, 1134 Park Street, Hatfield, Pretoria 0028, South Africa
4. Discipline of Agricultural Economics, School of Agriculture, Earth and Environmental Sciences, University of Kwa-Zulu-Natal, Private Bag X01 Scottsville, Pietermaritzburg 3209, South Africa
5. Department of Agricultural Economics and Extension, North-West University, Mmabatho 2790, South Africa