The other day I introduced a simple model of how a monetary economy works. The model was centred on the payments of my personal calling cards to elicit labour from the kids that live in my house. All the basic national accounting results that apply in a real economy were present. The simplicity extended to considering only two sectors – the kids (private) and the “house” (public). In terms of modern monetary theory (MMT) we start by examining the broad relationships between the government and non-government sector, where the latter comprises the private domestic and foreign sector. Some readers have suggested that the results obtained would not apply if I had have explicitly modelled the cross-border flows (that is, the external sector). Well today, I have some news … some neighbours have arrived next door to my place and the kids from each house are jumping fences.