The reason that the area which could potentially become CANZUK looks bad in present statistics is because Britain is still a member of the EU and CANZUK does not presently exist.
As a member of the protectionist EU, we are forbidden to enter into free trade agreements with the other potential members of CANZUK. The EU has finally signed a free trade agreement with Canada in 2016, 12 years after agreeing to form it. To date, CETA is not yet in force.
The EU is responsible for considerable damage to the UK’s trading relationship with the rest of the world because the EU is essentially a prison in which the inmates cannot form mutually beneficial trade relationships with anyone outside the prison, and have to endure severe economic harm waiting for the creakingly sclerotic bureaucracy of their unelected EU masters to crawl into action.