There is no Bitcoin Federal Reserve. New Bitcoins can't be printed at the rate of adoption. And there are certain whales who can singlehandedly affect the price.

Look at the exchange order books and they are thin enough for daily swings to be pretty huge. The market has not matured to the point where there are large reserves preventing a move in any particular direction.

And lately, there has been so much new money coming in, the sellers can't even remotely keep up. So the value has changed quickly, but mostly in the positive direction.