Like most commodities, the price of silver is driven by speculation and supply and demand. Compared to gold, the silver price is notoriously volatile. This is because of lower market liquidity, and demand fluctuations between industrial and store of value uses. At times this can cause wide ranging valuations in the market, creating volatility.
Silver often tracks the gold price due to store of value demands, although the ratio can vary. The gold/silver price ratio is often analyzed by traders, investors and buyers. In Roman times, the price ratio was set at 12 or 12.5 to 1. In 1792, the gold/silver price ratio was fixed by law in the United States at 15:1, which meant that one troy ounce of gold was worth 15 troy ounces of silver; a ratio of 15.5:1 was enacted in France in 1803. The average gold/silver price ratio during the 20th century, however, was 47:1. Physical silver is sold with a premium that is always higher than the spot price, the instantaneous price as quoted in a newspaper or on a website. In most cases the premiums for physical silver are about ten percent or higher, with extra fees for shipping and storage as well.
Article Source: en.wikipedia.org