From a supply perspective, the United States Geological Survey states that silver is nearly twice as rare as gold in the long term because it is not recycled at the same rates as gold. Also, at current consumption rates, all of the silver that is in the earth's crust will diminish away in the next 25 years. This will likely put supply pressures on the price of the metal.
A combination of these factors will likely provide support to silver prices; the following ETFs should reap the benefits:
iShares Silver Trust
(SLV), which physically holds silver bullion and closed at $18.27 on Wednesday.
PowerShares DB Silver Fund (DBS), which holds futures contracts in silver and closed at $33.16 on Wednesday. PowerShares Ultra Silver (AGQ), which seeks to gain twice the performance of silver bullion and closed at $68.06 on Wednesday.