Brokers said that the BRL1.55 level lost support when banks and corporate holders of dollar forwards and futures gave up on holding the dollar given the current debt impasse in the US. Holding a dollar forward valued at BRL1.55 when the dollar weakens to BRL1.50 is a money losing proposition.

FORBES: Dollar Weakens Against Brazil Currency; Lowest Level in 12 Yrs

The final key, I think, for market direction going forward is the dollar.

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Fast forward to the dollar and the yuan in recent years.

FORBES: Currency Manipulation