Swiss francs are up, the ruble is down, and the euro is sliding back to levels not seen in over a decade.
So what exactly, makes the value of a currency rise or fall?
The short answer: The price is set minute by minute by traders and investors who make bets on which way the market prices of a currency is headed. But there are more powerful, longer-term forces at work driving those bets.
A country's currency is, in part, a reflection of how well or poorly its economy is doing. And, for the moment, the U.S. is setting the pace for the rest of the world. U.S. gross domestic product surged at 5 percent annual rate from July through September (the latest reading available), the fastest pace in more than a decade. As the recovery picked up speed last year, American employers added nearly 3 million jobs to their payrolls, the biggest gain in 15 years.
Investors around the world looking for a piece of that growth have to use dollars to buy into it. And that demand for dollar-based investments drives up the price. In the second half of last year, the dollar rose more than 16 percent against a collection of world currencies.