For most animal welfare concerns there is at least some degree of overlap among the different viewpoints. When measures arising from different viewpoints lead to the same conclusions it is much easier to reach consensus in interpretation. This is especially true when reduced productivity corresponds with other measures, since the evidence also provides economic incentive for alleviating a welfare concern. Most recommendations for floor space allowance for growing-finishing pigs, for example, are based on measures of productivity (Gonyou, et al 2006). However, productivity rates do not always correspond with other measures of welfare – for example when a lame sow who finds it painful to stand or walk delivers and weans a large, healthy litter of piglets. In many respects, intense selection for high levels of  production has created a mismatch between productivity and other aspects of biological fitness. For example, breeding sows have to be feed-restricted in order to maintain high reproductive rates, yet they show signs of chronic hunger on the diets commonly provided. There are also examples where selection for fast lean growth has also led to producing pigs that may be more aggressive, more difficult to handle or are more susceptible to handling stress. Disagreements
among the viewpoints, especially when different scientific measures conflict lead to the most contentious debates concerning animal welfare.