When Trade Minister David Parker signed the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP) in Chile on 8 March it came just a few weeks after the Labour-led coalition government released a National Impact Assessment of the deal. In a series of interviews Parker argued that Labour was signing TPP-11 for pragmatic reasons (he gave the agreement a ‘7 out of 10’). Walking away from the deal, he said, would mean New Zealand would suffer a net-loss from a decline in investment and trade opportunities. The evidence Parker cited was largely based on the country's prior preferential trade agreements (PTAs). For example, he said the 2008 New Zealand–China Free Trade Agreement (NZCFTA) was the reason for the huge increase in trade and investment between the two countries in the last decade.
But how persuasive are Mr. Parker’s claims? Without detailed post-hoc modelling it is near impossible to credibly infer causality between New Zealand's PTAs and aggregate trade growth. A host of variables may be responsible, from changing migration patterns to a shift to consumption-based growth. Australia, which only signed a PTA with China in late 2015, saw its own trade quadruple during the previous decade. In light of this, can New Zealand credibly attribute our success to the NZCFTA? And what does this mean for claims made about the CPTPP?