With very attention-grabbing efficiency outcomes.
It should’ve been previous midnight. I don’t bear in mind the place (possibly Medium?), however I discovered one might use Google Finance’s API inside a web based spreadsheet to question inventory value knowledge. 🤯 So, half-heartedly, I question some knowledge and begin taking part in 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 conduct, and lastly, there appears to be an exponential progress/decay issue at play (a long-term pattern, if you’ll). Furthermore, it appears there are occasions when the value of the index and the value of the ETF fluctuate 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 a little bit extra, I discovered that in sure elements of the 12 months — 4 occasions EVERY YEAR in reality, since 2013 — the value of the connection comes off shortly, it often takes +/- 5 days to finish, then the rest of the interval the value 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 value of the funding drops, it implies the S&P500 weakens relative to the ETF. Or you might 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 can 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 all the time skeptical of evaluating outcomes. It’s the traditional, “You can’t 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 will get pleasure from it— you simply can’t try this.
In fact, I’m going to interrupt that rule, as a result of this text wouldn’t be as attention-grabbing. It could be priceless to test much more ETFs (than SPY) to see if it is a phenomena that happens in additional locations than one. Should you try 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 after we assume the connection will drop, then we’d flip our place to brief. Bear in mind, I discussed this happens 4 occasions yearly and just for a +/- 5 days, so the technique might 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 believe because of this we see the weighted win p.c larger than the (unweighted) win p.c. It could be good to measurement positions in line with the chance of upper beneficial properties.
Once more, the wager of this technique is, for a lot of the 12 months, the S&P500 will strengthen relative to the ETF, and infrequently, we flip the logic of the wager.
Why does this conduct exist? What forces drive the continued divergence and fast reversion at totally different occasions of the 12 months (and the very same occasions from 12 months to 12 months)?
Evaluation
Let’s take a step again, now that we perceive the technique a little bit higher, and critically take into consideration what these outcomes inform us.
The annualized PL / max each day drawdown in addition to annualized PL/worth in danger each look nice. However, the most important challenge 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 median 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 type of cash on this technique, in a full 12 months — assuming I wish to make $10K — then I have to allocate $667K for the entire 12 months.
I don’t even assume it’s value pursuing the evaluation additional. Do you?
Closing Ideas
On this article we mentioned a very attention-grabbing arbitrage between the S&P500 and considered one of its ETF’s: SPY. The technique we employed appeared promisingly predictive. After we evaluated the selections the technique would have informed us to make by historical past, we discovered the efficiency seemed wonderful. Put into context, after reviewing abstract statistics, we discovered it could take a considerable amount of capital to make any cheap amount of money for somebody like me.
The query I’m left with is, “Wouldn’t it be definitely worth the funding?”
Go away your ideas within the feedback beneath. I might 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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