Volatility hasn't crept back into the markets; it has jumped back in. The COVID-19 coronavirus outbreak has sent stocks lurching over the past week. And in the face of such huge market swings, investors sometimes make rash decisions that can ultimately harm their portfolios. That's where exchange-traded funds can help - specifically, low-volatility ETFs.

Big declines trigger fear, and that fear will be even more elevated when it's triggered by something like a genuine health crisis. People don't want to lose money, and they certainly don't want to lose more money than they already have. While you should always be looking for stocks to sell as a matter of regular portfolio maintenance, if you panic-sell, you risk throwing the baby out with the bathwater.

In many cases, investors who jettison their stocks en masse on the way down cement their losses while leaving themselves out of the recovery.

Here are nine low-volatility ETFs that might help ward off this instinct and lessen your pain. Low-vol (and "min-vol") funds use different strategies in the name of providing portfolios that are more stable than the broader market. That not only helps muffle losses during downturns, but the reduction in volatility can give you a little peace of mind and let you participate in an eventual bounce-back. Take a look.

Invesco S&P 500 Low Volatility ETF

There are two basic types of volatility ETF: low-volatility ETFs and minimum-volatility ETFs. Let's start with the first.

The Invesco S&P 500 Low Volatility ETF (SPLV, $58.39) is a pretty straightforward fund that tracks the S&P 500 Low Volatility Index, which is composed of the 100 S&P 500 components with the lowest realized volatility over the past 12 months. It then assigns weights to each stock based on its volatility (well, lack thereof).

A popular gauge of volatility is beta, which tracks a security's volatility compared to some benchmark. The benchmark in this case is the S&P 500, and the benchmark will always have a beta of 1. SPLV has a beta of 0.58, which means the fund is moving up and down considerably less than the broader market.

That's exactly what you want to see when the market is heading lower. For instance, between Feb. 19 and Feb. 27, as the S&P 500 declined 8%, the SPLV only declined by 5.2%. During the near-bear market in Q4 2018, the S&P 500 declined by 19.3% at its nadir - SPLV lost only 10%.

The portfolio is bound to change over time depending on which parts of the market are more volatile than others, but for now, it's unsurprisingly heavy in utility stocks (27.4%) and real estate investment trusts (REITs, 18.0%) - two defensive, high-yielding sectors. Top individual holdings include utilities such as Duke Energy (DUK) and Eversource (ES), as well as waste collection company Republic Services (RSG).

Learn more about SPLV at the Invesco provider site.

iShares Edge MSCI Min Vol USA ETF

Minimum-volatility ETFs work a little differently.

Rather than simply taking a portfolio of the lowest-volatility stocks within an index, min-vol funds will evaluate volatility, but other metrics too, such as correlation (how a security moves in relation to the market). They'll also sometimes try to keep sector weightings and other factors close to the original index they're working with. The idea is to put together a portfolio that minimizes risk. But because of that, min-vol ETFs sometimes will hold stocks with relatively high volatility (such as gold miners).

If it's hard to tell the difference, think about it this way: Min-vol ETFs try to provide a low-volatility basket of holdings. Low-vol ETFs try to provide a basket of low-volatility holdings.

Enter the iShares Edge MSCI Min Vol USA ETF (USMV, $65.92).

USMV applies a multi-factor risk model, which examines traits such as value and momentum, to the MSCI USA Index, which includes large- and mid-cap stocks. But it also applies a maximum cap weight for every stock (2%, or 20x the stock's weight in the S&P 500, whichever is lower), and its sector weight must be within 5% of the benchmark's standard weight. The goal, then, is to build a portfolio that's less volatile than the broader market, but it's not just selecting the absolutely least volatile stocks to do it.

The result is a portfolio you might not expect. Technology stocks are the largest part of the fund, at 17.7%, followed by financials at 16%. Utilities and real estate are actually closer to the middle of the pack, at more than 8% apiece.

Top holdings, though, include plenty of low-beta names. Gold stock Newmont Mining (NEM), utility NextEra Energy (NEE) and Coca-Cola (KO) top the fund at weights of 1.6%-1.9%. And indeed, USMV has a low beta overall, at 0.65.

Learn more about USMV at the iShares provider site.

Fidelity Low Volatility Factor ETF

The Fidelity Low Volatility Factor ETF (FDLO, $38.07) culls its picks from a universe of the 1,000 largest U.S. stocks based on market cap, which again ends up resulting in some mid-cap holdings.

Fidelity tries to select the least volatile companies by considering three factors equally:

• Five-year standard deviation of price returns: Measures long-term price volatility, favors stocks with lower standard deviations
• Five-year beta: Measures stock sensitivity to market movements, favors stocks with lower beta
• Five-year standard deviation of EPS (earnings per share): Measures volatility of corporate profits, favors stocks with lower standard deviations of profits

Technology looms large in this portfolio at nearly 24%. Five other sectors have weights between 9% and a little more than 13%. What's interesting is that traditional "defensive" sectors have little representation: Consumer staples, utilities and real estate combine to account for just less than 13% of assets under management (AUM). Other low-volatility ETFs treasure those sectors.

FDLO does consider market capitalization when weighting the stocks (larger companies make up a bigger part of the fund), but it also uses an "overweight adjustment" to keep any one company from having too large an influence on the fund. For example, $1.3 trillion Microsoft (MSFT) makes up 5.0% of the fund, while $294 billion Mastercard (MA) comprises 1.5%. Thus, Microsoft is 4.4 times bigger than Mastercard, but accounts for just 3.3 times the AUM.

Learn more about FDLO at the Fidelity provider site.

Invesco S&P MidCap Low Volatility ETF

Several of the market's hottest growth stocks over the past few years have been mid-cap stocks - between $2 billion and $10 billion - at some point. But collectively speaking, mid-caps don't get nearly the attention their smaller and larger brethren do.

That's too bad. Because mid-cap stocks tend to outperform both over time, and that outperformance looks even sweeter when you consider their risk relative to large and small companies.

Low-volatility ETFs such as the Invesco S&P MidCap Low Volatility ETF (XMLV, $52.02) reduce your risk in mid-caps in two additional ways: by spreading it across dozens of stocks, and by focusing on low volatility. Specifically, XMLV holds the 80 lowest-volatility stocks in the S&P MidCap 400 Index.

Like its large-cap sister fund, SPLV, XMLV is heavy in real estate and utilities - in fact, those two sectors account for more than half the fund's assets, at 32.0% and 20.1%, respectively. It also has a significant 17.9% weight in financials. It has almost no exposure to communications and technology, and it has zero energy exposure.

Learn more about XMLV at the Invesco provider site.

Legg Mason Low Volatility High Dividend ETF

Some low-volatility ETFs throw in other small tweaks. For instance, the Legg Mason Low Volatility High Dividend ETF (LVHD) $32.60) is one of a handful of low-vol funds that are looking for stable stocks, but within a universe of high-yielding dividend payers.

It makes sense. Low volatility swings both ways. Sometimes having stocks that are more volatile than the market is advantageous - if the market is going up, but your stocks are going up even more rapidly, for instance. And sometimes reducing volatility actually limits your price gains. But you can make up some of the difference if you're also drawing returns in the form of largest dividends.

LVHD starts with a universe of stocks that's considerably larger than most of these other funds; at 3,000 U.S. stocks, the list inevitably includes mid- and even small-sized companies. It then narrows the list down to profitable companies that can pay "relatively high sustainable dividend yields." It then looks for price and earnings volatility - the lower those metrics are, the better the score, and thus their weight in the fund.

LVHD rebalances quarterly, and when it does, no stock can account for more than 2.5% of assets. Sectors are capped at 25%, though REITs are capped at 15%.

This ETF typically holds between 50 and 100 stocks, though the number is 80 at the moment. The "big three" defensive sectors - utilities, real estate and consumer staples - account for nearly 59% of the fund's assets, which helps it yield nearly twice what the S&P 500 collectively pays out. Top 10 holdings include the like of telecom infrastructure REIT Crown Castle International (CCI), power management company Eaton (ETN) and Clorox (CLX) - a consumer staples play that has done extremely well amid the coronavirus threat.

Learn more about LVHD at the Legg Mason provider site.

Invesco S&P International Developed Low Volatility ETF

Investors typically like to have at least some exposure to international stocks to help hedge against any downturns in U.S. equities. But plain-Jane international exposure doesn't do much to defray the risk when markets all over the world are shaking, as they have been amid the COVID-19 threat.

The Invesco S&P International Developed Low Volatility ETF (IDLV, $33.06) is a way to remain invested overseas while trying to reduce some of the volatility that Japan, Western Europe and other developed regions of the world are experiencing.

It's not a bad way to collect yield, either.

The IDLV tracks the S&P BMI International Developed Low Volatility Index, which is made up of roughly 200 constituents across several developed-market nations. It then assigns weights to the stocks based on their realized volatility over the trailing 12 months - again, the lower the volatility, the higher the weight.

At present, IDLV is invested in stocks from 10 developed nations. Canada (24.7%) and Japan (21.7%) make up the largest concentrations, with Singapore comprising another 7.8% of assets. Real estate (21.5%) and utilities (13.8%) are well-represented, but the highest allocation of assets goes to financials, at 26.4%. That's largely because of heavy weights to several Canadian bank stocks, including National Bank of Canada (NTIOF), Royal Bank of Canada (RY) and Bank of Nova Scotia (BNS).

The other bonus? International large-cap stocks tend to yield more than their American counterparts, and as a result, this collection of low-vol plays yields a massive 5.5% right now.

* Includes a 10-basis-point fee waiver

Learn more about IDLV at the Invesco provider site.

iShares Edge MSCI Min Vol Emerging Markets ETF

You can also use low-volatility ETFs to get calmer results out of more volatile areas of the market.

The iShares Edge MSCI Min Vol Emerging Markets ETF (EEMV, $54.10) holds nearly 350 stocks domiciled in "emerging" or "developing" countries. Countries such as the U.S., Japan and Canada are considered "developed" - they have established, relatively stable markets, with not a lot of geopolitical risk, but also, growth tends to be less robust in these kinds of nations. Emerging markets, on the other hand, typically feature better growth profiles, but less reliable markets thanks to risks such as volatile country leadership, risk of corruption and fewer stock-market regulations.

The EEMV is one of a few ways that less risk-averse investors can still get exposure to the high growth of emerging markets. EEMV spreads your risk across hundreds of holdings, and across a dozen countries, selecting companies based on their low-volatility characteristics. Better still, single-stock risk is minimized, with no individual company holding more than a 1.7% weight.

Like most emerging-market funds, EEMV is heavily invested in China (29.3%), which is naturally problematic given that's the epicenter of the COVID-19 outbreak. Taiwan is another 17.3%, and South Korea is 6.4%. Still, the EEMV has held up better than its traditional counterpart, the iShares MSCI Emerging Markets ETF (EEM), so far through the coronavirus-inspired downturn. Perhaps more encouragingly, it has outperformed EEM by more than 12 percentage points on a total-return basis since the fund launched in October 2011.

* Includes a 43-basis-point fee waiver.

Learn more about EEMV at the iShares provider site.

First Trust Dorsey Wright Momentum & Low Volatility ETF

The First Trust Dorsey Wright Momentum & Low Volatility ETF (DVOL, $23.01) is a mouthful, and it might sound like a paradox at first, but it's an interesting fund that holds up well during down markets but also is plenty competitive when stocks begin to heat up again.

But its methodology is a little complicated.

Every quarter, the index starts with the constituents of the Nasdaq US Large Mid Cap Index (large- and mid-cap stocks) that meet certain basic eligibility criteria such as a minimum average daily dollar volume of $1 million for the previous 30 days. It then looks for stocks that have strong price momentum compared to the broader market, then selects the 50 least-volatile stocks from the trailing 12 months. Stocks with the lowest volatility make up the fund's largest weights.

More succinctly, DVOL is taking a momentum strategy - essentially buying stocks that are performing relatively well - and pairing it with low volatility.

DVOL has a 39.2% weight in utilities and another 26.3% in real estate. Financials are another huge chunk, at 18.3%. Several sectors, including energy and communications, aren't represented at all.

This strategy has led to market outperformance not just during downturns like the market's quick recent drop and the Q4 2018 plunge, but also over the long haul. DVOL has outperformed the trailing one-, three- and five-year periods.

Learn more about DVOL at the iShares provider site.

IQ S&P High Yield Low Volatility Bond ETF

While most low-volatility ETFs invest in the stock market, the IQ S&P High Yield Low Volatility Bond ETF (HYLV, $25.36) is one of a few rare bond funds that try to tame fixed income.

The HYLV attempts to straddle the gap between the high yield of below-investment-grade ("junk") bonds and their relatively high risk. It tracks an index that selects bonds using a calculation that factors in the bond's duration (which measures a bond's sensitivity to interest rates), the bond's spread (the difference between its yield and the yield of a U.S. Treasury bond with a similar maturity) and the spread of the broader universe of bonds HYLV selects from.

At the moment, 38.7% of the fund's holdings are rated B (the second-highest level of junk debt) and 37.2% are BB (the highest level). About 12% of its portfolio is rated below B, and roughly 10% is in investment-grade debt.

That's safer, overall, than the portfolios of popular junk-bond ETFs such as the popular SPDR Bloomberg Barclays High Yield Bond ETF (JNK) and iShares iBoxx $ High Yield Corporate Bond ETF (HYG). But the trade-off is a lower yield than either of those funds. To its credit, it has performed better than JNK and HYG on a price basis since inception in February 2017, but their total returns have been slightly better.

* Includes a 1-basis-point fee waiver

** SEC yield reflects the interest earned after deducting fund expenses for the most recent 30-day period and is a standard measure for bond and preferred-stock funds.

Learn more about HYLV at the New York Life provider site.

JPMorgan Ultra-Short Income ETF

The JPMorgan Ultra-Short Income ETF (JPST, $50.59) doesn't follow a low-volatility index, a minimum-volatility index, a minimum-variance index or any of that.

But the very nature of what it does invest in makes JPST a low-volatility ETF nonetheless.

JPMorgan Ultra-Short Income ETF holds a little more than 700 bonds with an average duration of less than one year. That effectively means that the portfolio will go down a mere 1% for every 1-percentage-point hike in interest rates.

JPST's holdings are extremely low-risk. The average effective maturity of the bonds it holds is a little over a year. All of them are investment-grade, and about 80% of them receive A ratings or higher. That said, nearly two-thirds of the bonds are corporates, rather than even safer Treasuries and other agency debt, so it's still able to pay out a yield of 1.9%.

That might sound modest, but consider that this fund is effectively planted in the ground, good or bad. Since inception in May 2017, the difference between its lowest low and highest high is a mere 1.2%! Compare that to the 11% maximum difference in the iShares Core U.S. Aggregate Bond ETF (AGG), which tracks the effective benchmark for bond funds.

That makes JPST a solid place to park some funds until the world looks a little safer.

Learn more about JPST at the JPMorgan Asset Management provider site.

Kyle Woodley is Senior Investing Editor at Kiplinger.