The old "frienemies" are usually on the other sides of the financial swings and roundabouts. Usually when the US dollar weakens, the Euro rises in relation. On the other hand, when the US dollar rises Euro’s value declines in relation.
The US economy often experience increasing unemployment rate resulting in weakening of the US dollar. If this information is available and unemployment rate is confirmed the forex traders will buy (ask) the Euro with the anticipation that it will appreciate vs. the dollar.
Conversely, if there is a rush in demand for US financial instruments like treasury bonds or equities, this pushes the US dollar up with regard to the Euro. In this case, the forex traders sell (Bid) the Euro since the value of US dollar will appreciate.
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