Effective ETF Investing Strategies


Long-Only and Long & Short

Shorting versus Inverse ETFs

Inversion and Submersion


Sometimes, what you don’t know can kill you. Yes, even in the relatively controlled world of ETF investing!

For example, the Cabot ETF Investing System that I edit runs two strategies, Long-Only and Long & Short.

The Long-Only strategy alternates between owning ETFs of “Favored” S&P sectors (in up-trends) and holding cash (in down-trends).*

The Long-Short strategy for more aggressive portfolios holds those same Favored sectors in up-trends, but sells short** the S&P tracking ETF, S&P 500 SPDR (SPY), in downtrends.

But some investors—generally those with retirement accounts—are not allowed to sell short. So from time to time, these people ask me whether they can use an inverse S&P proxy like the ProShares Short S&P 500 (SH) to capture gains in a downtrend.

Using an inverse ETF seems like an effective strategy on the surface, but I generally advise against it, and here’s why.

An inverse ETF like SH will do very well (gain value) when the market goes straight down. (And of course it will lose money just as readily if the market goes straight up.) But markets rarely go straight up or down. And even more rare would be to actually know in advance when the market will go straight down. We simply don’t know that much.

The best we can know is the probability that an uptrend or downtrend will continue. And even when our probability proves correct, most of the time the market will move in some kind of zig-zag or on-and-off pattern. And those zig-zag fluctuations work against the inverse ETF.

Here’s why. Because tracker ETFs seek to replicate their underlying indexes, the underlying stock portfolios (stocks held in the ETFs) are rebalanced daily. And the compounded returns of rebalancing cause a little erosion when the market fluctuates.

Consider a $10,000 investment in an inverse S&P ETF. Your investment controls $10,000 of the underlying index portfolio. That value will expand when the S&P goes down, and contract when the S&P goes up.

Suppose the index goes down by 1% one day and then bounces back to where it was the next day. That second day advance is slightly larger in percentage terms…approximately 1.01%. (100/99 difference from 1.00 is bigger than 99/100 difference from 1.00.)

So at the end of the first day, your original $10,000 is up 1% and is worth $10,100. Then the second day your ETF is down 1.01% of the $10,100, which is about $101. So the index is unchanged for the two-day span, and you’re down $1, holding only $9,999.

An actual short-sale would have returned your original $10,000 on the second day, but the inverse ETF eroded a little.

That kind of erosion goes on in inverse ETFs and (even more) in leveraged ETFs. The short-term up-and-down action (or down-and-up) nets a loss.

The same erosion effect grinds on as long as there is fluctuation—which is almost always—and the bigger the fluctuation (volatility), the steeper the erosion.

If the fluctuation is trending down (instead of flat like the example), the erosion is masked, and the trend gain can outweigh the volatility erosion. But the erosion continues as long as the fluctuation continues, eating away at your returns, even if you’re right about the market’s trend.

But that doesn’t mean inverse ETFs are always bad!

Inverse ETFs are useful tools when there is reason to expect prompt decline in an index. For instance, they’re useful if you expect a bad economic report in the coming days, or if some technical market indications suggest imminent weakness. Such a bet will be right or wrong (depending on your insight and analysis), but will not suffer from debilitating erosion, because you’ll have the answer very shortly.

The Cabot ETF Investing System makes a different kind of directional bet. When the Cabot Tides and 3-D indicators turn negative, the Sell signal is not a time-specific prediction of decline. Rather, a Sell signal says that market conditions are likely to bring a decline over the coming weeks or sometimes months. We don’t know how long the decline will take to get started, and we don’t know how long it will last, but we do know that our signals add value over time, and thus the system will pay off if we simply stick with it. And while there most surely will be up and down wiggles in the meantime, we won’t be penalized for them!

Investors who try to modify our system by substituting inverse ETFs for the short position may find that the inversion ETF becomes a submersion ETF. At the very least, it will reduce gains and increase losses.

Get more information on Cabot ETF Investing System here. 

Your guide to ETF investing,

Robin Carpenter
Editor, Cabot ETF Investing System

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