Ainda o "border adjustment tax"

The shocking truth about border tax adjustments, por Scot Sumner (Econlog):

A US border adjustment tax would be a massive contractionary shock for the global economy. The only question is what type of shock. Here are three possibilities:

A. The dollar appreciates by 25%.
B. The dollar is unaffected.
C. The dollar appreciates by 12.5%.

In case A, trade is unaffected, but foreigners with dollar denominated debts would immediately see their debts rise by 25% in local currency terms. This could create a global financial crisis.

In case B, dollar debtors would be unaffected, but you would have a massive trade shock. The real (after tax) exchange rate for foreign countries would immediately appreciate by 25% relative to the US dollar. Over time, equilibrium would be restored through a painful process of reducing wages and prices in foreign countries, until the real exchange rate moved back to equilibrium.

In case C, you have a fairly sizable debt shock and a fairly sizable trade shock at the same time. Emerging market exporters would lose exports at exactly the same time that their dollar denominated debts rose by 12.5% in local currency terms. Not good.

I've been trying to wrap my mind around the question of why this border tax would be such a big shock. I think it might have something to do with the fact that money inflows to the US caused by the export of Boeing jets would receive a 20% subsidy, but money inflows to the US in repayment of dollar debts would not receive any subsidy. Perhaps someone who knows more about border taxes/subsidies can clarify this issue.

A parte do "I've been trying to wrap my mind around the question of why this border tax would be such a big shock. I think it might have something to do with the fact that money inflows to the US caused by the export of Boeing jets would receive a 20% subsidy, but money inflows to the US in repayment of dollar debts would not receive any subsidy" e o comentário (em parte incorreto) de um leitor dizendo que "I also think that the standard text book model assumes that all currency flows are driven by real trade flows: there is little emphasis on the capital and financial system. Given that capital flows are so large nowadays, I find the full currency adjustment theory somewhat unrealistic" parecem ir num sentido parecido ao do meu post - que o que complica tudo são os movimentos internacionais de capitais.