What is the driving force for these moves? The "carry trade."
What is the carry trade? It's the borrowing of a currency in a low interest rate country, converting it to a currency in a higher interest rate country and investing it in the highest rated bonds of that country. The big trading outfits do this with leverage of 100 or 300 to one. This causes important moves in the financial markets, made possible by the trillions of dollars of central bank money creation.
The monetary stimulus in Japan is aimed to produce a cheaper yen, and thus a stronger dollar. That causes the U.S. bond market to rise, bond yields to decline, commodity prices to plunge, and precious metals prices to decline. If you are in any of these investments, you must know what drives their prices.
Here is how the "yen carry trade," a favorite currency for the trade, basically works now:
Hedge funds and other very big traders borrow the yen at very, very low interest rates now approaching zero.
The yen are converted to dollars, which are invested in U.S. Treasuries at a much higher yield than the interest cost for the borrowed yen. That creates a "positive carry" because of the differential in interest rates.
The buying drives up U.S. bond prices. The traders accrue big profits, when done with high leverage, assuming the yen value doesn't rise.
Additional profits are made when a) The dollar rises vs. the yen as the BOJ intends, b) U.S. Treasuries rise in price (as is happening)