1. Department of Agricultural Sciences, Lincoln University, Lincoln 7647, New Zealand
2. School of Accounting, Finance and Economics, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
3. AgResearch, Private Bag 4749, Christchurch 8140, New Zealand
4. School of Agriculture and Environment, Massey University, Private Bag 11 222, Palmerston North 4442, New Zealand