It's been a volatile year for the stock market, with some notable market leaders still struggling to get back to their baselines. In particular, biotech stocks and money center banks have largely underperformed in 2016.

That hasn't been the case for physical precious metals or precious-metal mining stocks, which are among the year's top performers. With physical gold up more than $250 an ounce year-to-date (24%), 14 of the 22 gold mining stocks that have market valuations of $300 million-plus have more than doubled in 2016. Upward momentum has been even more pronounced among physical silver and silver mining stocks. Spot silver prices are up better than $5 an ounce (37%) year to date, with all six of the silver miners valued at $300 million or more at least doubling in price. These stocks are the true standouts this year.

The bullish case for silver

When we take a step back and analyze the catalysts behind the move higher in precious metal spot prices, it's silver that could have considerably more upside than gold. Today, we'll lay out the case why physical silver could be on its way to $30 an ounce, which would represent a gain of nearly 60% from where physical silver is today.

Growing demand

Silver is often thought of in the same context as gold in that it's a hedge investment that people flock to during times of uncertainty. However, what's often overlooked is that supply and demand can have just as much impact on spot metal pricing as investor sentiment.

According to the World Silver Survey 2016, published by the Silver Institute earlier this year, total supply in 2015 worked out to 1.04 billion ounces, but demand increased year-over-year by 39 million ounces to 1.17 billion ounces. This works out to a physical deficit of roughly 130 million ounces of silver, which represents the second-largest deficit since 2008.

The report notes that demand for silver in solar panels (silver is an excellent conductor of electricity and heat) grew by 23% year-over-year to 77.6 million ounces, with investor demand for bars and coins surging by more than 56 million ounces to 292.3 million ounces in 2015. Demand from the jewelry and silverware industries also improved modestly.

With total physical demand for silver having grown by 17% since 2012, and silver prices having fallen by nearly half over that time span, it's not surprising to see silver prices enjoying what appears to be a demand-driven rebound. As long as the physical demand for silver continues to rise, silver's spot price should have plenty of support and reason to head higher.

Low opportunity cost

Another factor working in favor of silver (and gold, for that matter) is the low opportunity cost trade-off between precious metals and interest-bearing assets. "Opportunity cost" means putting your resources into one asset and thus sacrificing the chance to potentially earn better returns elsewhere.

If we look back a little more than a decade to when banks' CDs and U.S. Treasury yields were paying out 5% or more, it would have been tough to convince investors to give up that near-guaranteed rate of return to instead buy silver, which has no dividend yield.

Today, however, the tables are turned. Bank CDs, Treasury yields, and savings accounts are all yielding very low rates that in some cases are lower than 1%. With return rates this low, investors could actually be losing purchasing power relative to inflation, even if they're logging nominal gains from an interest-based investment like a CD or bond. Buying silver in a low interest rate environment means investors aren't giving up very much in the way of opportunity cost since buying a CD or Treasury bond could cost them real money when inflation is factored in.

As long as the Federal Reserve continues to walk on eggshells with regard to interest rates, silver should remain a popular investment option among investors.

Closing the gold-to-silver gap

Turning to a slightly more psychological factor, I'd point to the gold-to-silver ratio as an important reason why physical silver could outperform going forward.

Generally speaking, physical gold is a considerably more liquid asset, with fewer dollars flowing into physical silver investments relative to gold. What this does is make physical silver more volatile than gold. This means silver often outperforms gold when times are good, and tends to substantially underperform gold when the fundamentals have turned against the industry.

Throughout the entirety of the 20th century, gold's per-ounce price was an average of 47 times that of silver's per-ounce price. More recently, with gold at $1,315 an ounce and silver at roughly $19 an ounce, the gold-to-silver ratio has been about 69. If silver were to simply narrow this difference and return to its 20th century average, this alone would move silver up to $28 an ounce.

Three silver miners well-positioned to take advantage of rising silver prices

Now that you have a better understanding of why physical silver could make a run at $30 an ounce, let's take a look at three silver miners that would be in prime positon to benefit from rising silver prices.

The obvious choice is Silver Wheaton (NYSE:WPM), which is a royalty and asset streaming company in the silver- and gold-mining space. In return for upfront capital that miners use to develop and expand their mines, Silver Wheaton receives long-term or life-of-mine contracts that allow it to purchase a specified amount of gold or silver at a fraction of the current spot price.

During the second quarter, Silver Wheaton took delivery of gold and silver at $401/oz. and $4.46/oz., respectively. This leaves Silver Wheaton with a margin of $900 an ounce on gold and nearly $15 an ounce on silver. Any increase in silver's per-ounce price will go directly to Silver Wheaton's bottom-line. Better yet, Silver Wheaton's dividend policy is tied to the rising (or falling) price of the underlying metals themselves. If silver rises substantially, so should Silver Wheaton's payout.

Forgive the clear bias, as it's a core holding in my portfolio, but Silver Standard Resources (NASDAQ: SSRI) stands to benefit in a big way. Silver Standard is benefiting from its recently closed acquisition of Claude Resources, which will add about 70,000 ounces of gold production annually, and is immediately accretive to earnings and cash flow.

What's most important for Silver Standard Resources is just how drastically it's been able to reduce its costs. The company has been shedding non-core assets and throwing its capital at only the most promising projects. Silver Standard has twice lowered its cash cost forecast in 2016, which bodes particularly well for its margins if silver prices continue to rise.

Lastly, Coeur Mining (NYSE:CDE) could be an intriguing investment opportunity considering its recent aggressive expansion. During the second quarter, Coeur Mining reported a 19% year-over-year increase in silver equivalent ounce production to 9.6 million ounces, largely driven by a 64% increase in tons milled at its flagship Palmarejo mine, and improved year-over-year silver ore grade.

Despite going full bore with Palmarejo, Coeur has also been quite stingy with its cash on hand. It wound up repaying $99 million toward a term loan in July, which reduced its debt by nearly 20% and will result in $9 million in annual interest expense savings. Growing production and falling costs are a great combination in an environment where silver prices could be headed higher.