Modelling the heterogeneous effects of stocking rate on dairy production: an application of unconditional quantile regression with fixed effects

摘要

This article analyses the effects of stocking rate on dairy production, using New Zealand dairy farm business data for the period 2005-2014. Unlike previous studies that assume a homogenous relationship between stocking rate and dairy production, we contribute to the literature by investigating the heterogeneous effects of stocking rate on milksolids production and applying an unconditional quantile regression model with fixed effects to control for unobserved farm-specific traits that are time invariant. The empirical results show that stocking rate exerts significant heterogeneous effects on milksolids production at different quantiles. In particular, we find that an additional increase in stocking rate (i.e. one cow/ha increase) increases milksolids production per hectare by between 17% and 25% but decreases milksolids production per cow by between 5% and 12%. In addition, we find that milking interval, dairy breed, farm labour, access to irrigation and farm location are important factors that increase milksolids production.