With very attention-grabbing efficiency outcomes.
It should’ve been previous midnight. I don’t keep in mind the place (possibly Medium?), however I realized one may use Google Finance’s API inside an internet spreadsheet to question inventory value knowledge. 🤯 So, half-heartedly, I question some knowledge and begin enjoying round. My go-to was the S&P500 (ticker: INDEXSP:.INX; known as SPX) and an equal ETF (ticker SPY).
Quick ahead a number of minutes, I’m wanting on the graph beneath.

Exploration
Three items stick out to me within the graph above: first, there appears to be cyclicality, then I see reversion habits, and lastly, there appears to be an exponential development/decay issue at play (a long-term pattern, if you’ll). Furthermore, it appears there are occasions when the worth of the index and the worth of the ETF range in direction of and away from one another — there appears to be an arbitrary, slow-moving, center level.
From this, I soar to the conclusion this could possibly be a worthwhile discovering.
Quick ahead somewhat extra, I discovered that in sure elements of the 12 months — 4 occasions EVERY YEAR the truth is, since 2013 — the worth of the connection comes off rapidly, it normally takes +/- 5 days to finish, then the rest of the interval the worth of the connection slowly creeps upward, solely till it comes off once more.
For extra context, I take the S&P500 away from an element of the ETF, so when the worth of the funding drops, it implies the S&P500 weakens relative to the ETF. Or you could possibly state it within the reverse, the ETF strengthens relative to the S&P500 throughout that interval.
Moreover, it doesn’t matter which leg is doing the work, as a result of the funding is predictable. Now, understanding which leg is more likely to do the work could be an much more worthwhile technique, however we’ll depart that on the desk for now.
Preliminary Analysis
In a state of affairs like this, the place we observe a sample with all our knowledge, I’m at all times skeptical of evaluating outcomes. It’s the basic, “You can not use the identical knowledge level for rigor, if it was used for inspiration.” Doing so is akin to tasting a beverage first earlier than hypothesizing whether or not or not you’re going to take pleasure in it— you simply can not do this.
In fact, I’m going to interrupt that rule, as a result of this text wouldn’t be as attention-grabbing. It will be beneficial to verify much more ETFs (than SPY) to see if this can be a phenomena that happens in additional locations than one. When you do this work, please give your insights within the feedback beneath.
The technique right here is to be lengthy the funding the big majority of the 12 months, besides once we suppose the connection will drop, then we might flip our place to brief. Bear in mind, I discussed this happens 4 occasions yearly and just for a +/- 5 days, so the technique shall be brief for 20–30 days per 12 months and lengthy the remainder of the 12 months. The efficiency of this technique is proven within the graph beneath.

Stats: Win%=57.4; WghtWin%=64.2; AvgAnnPL=77.4; AvgAnnVaR=3.9; MaxDraw=26.2; AnnPL/MaxDraw=3.1; AnnPL/VaR=23.9; AnnPL/$Inv=0.015
It appears the technique performs higher, in a shorter window, throughout the massive drops within the funding. I feel for this reason we see the weighted win % greater than the (unweighted) win %. It will be good to dimension positions in keeping with the likelihood of upper good points.
Once more, the guess of this technique is, for many of the 12 months, the S&P500 will strengthen relative to the ETF, and now and again, we flip the logic of the guess.
Why does this habits exist? What forces drive the continued divergence and fast reversion at completely different occasions of the 12 months (and the very same occasions from 12 months to 12 months)?
Assessment
Let’s take a step again, now that we perceive the technique somewhat higher, and critically take into consideration what these outcomes inform us.
The annualized PL / max day by day drawdown in addition to annualized PL/worth in danger each look nice. However, the most important difficulty I’ve with the efficiency stats is the annual PL/cash invested. 0.015 is horrible. That worth means I’ll make 1.5% of no matter I make investments, in a mean 12 months. Common Annual PL says we’ll make $77, however I’ve to take a position, on common, $5,133. So, if I wish to make any sort of cash on this technique, in a full 12 months — assuming I wish to make $10K — then I must allocate $667K for the entire 12 months.
I don’t even suppose it’s value pursuing the evaluation additional. Do you?
Last Ideas
On this article we mentioned a very attention-grabbing arbitrage between the S&P500 and certainly one of its ETF’s: SPY. The technique we employed appeared promisingly predictive. After we evaluated the selections the technique would have advised us to make by historical past, we realized the efficiency regarded superb. Put into context, after reviewing abstract statistics, we realized it will take a considerable amount of capital to make any cheap amount of money for somebody like me.
The query I’m left with is, “Would it not be definitely worth the funding?”
Go away your ideas within the feedback beneath. I’d love for somebody to disagree with me.
***Please be suggested, I’ve not made any suggestions for buying and selling or investments. This text is for the reader — to not be taken as funding recommendation. Contact a monetary advisor for such inquiries. I’m not a monetary advisor.
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