Demand for silver.
Supply of silver.
Demand for the currency you are paying in.
Supply of the currency you are paying in.
ALL OF THE ABOVE, ALWAYS.
It is never just one factor, alter the balance of any of the above and you will see price movement.
The issue muddying the water is the financial worlds use of futures as a paper proxy for the real thing. All that ever does is drive the price too far, both up and down... remember that when we hit the highs, they will be as artificial as the lows thanks to paper and leverage.