Survivorship bias is the logical error of concentrating on survivors (successes) and ignoring casualties (failures).
When we do so, we miss the true "base rates" of survival (the actual probability of success) and arrive at flawed conclusions.
Survivorship Bias 101
History is written by the victors. But if we exclusively focus on these successes, we allow survivorship bias to distort our understanding of the world.
But what is "survivorship bias" and how does it work?
Here's Survivorship Bias 101!
👇👇👇
Survivorship bias is the logical error of concentrating on survivors (successes) and ignoring casualties (failures).
When we do so, we miss the true "base rates" of survival (the actual probability of success) and arrive at flawed conclusions.
Put simply, exclusively focusing on successes may actually inhibit our ability to identify (and replicate) the actions that led to such success.
An atheist named Diagoras is shown portraits of people who prayed and were saved from death at sea as proof of God's existence.
Diagoras replies, "I see those who were saved, but where are those painted who were shipwrecked?"
Survivorship bias can lead to a deeply-flawed understanding of cause-and-effect relationships.
Let's look at some examples.
The U.S. wanted to add reinforcement armor to specific areas of its planes.
Analysts plotted the bullet holes and damage on returning bombers, deciding the tail, body, and wings needed reinforcement.
By only plotting data on the planes that returned, they were systematically missing data on a critical, informative subset - the planes that were damaged and unable to return.
The "unseen" planes had sustained damage that was not.
Wald concluded that armor should be added to the unharmed regions of the survivors.
Where the survivors were unharmed is where the planes were most vulnerable.
Wald had identified the survivorship bias and avoided its wrath.
Where else do we see survivorship bias arise?
We all love business success stories. We love to read about companies and people who have achieved incredible success and fame.
We scan their backgrounds in desperate search of the actions or features that led to that success.
But these conclusions are flawed.
For every company that pursued a moonshot idea and is now worth billions, there may be 10 who did the same and collapsed.
Analysts may try to calculate the performance of funds or groups of stocks using only the survivors at the end of the period.
By ignoring closed funds or stocks removed from an index, we bias the data and overstate returns.
Flawed data ➡️ Flawed decisions
To actively fight this, we must study the features of both successes and failures.
The "seen" and the "unseen" are equally important in guiding our decisions.
So the next time you read a story of the hero who won, be sure to reflect on all of the heroes who lost, whose stories are not told.
Special thanks to @austin_rief of @MorningBrew, whose interesting tweet on new founders sparked this thread. https://t.co/ldSVsPP4uX
1/ New founders spend too much time trying to emulate mature companies they admire, and not enough time learning what those companies did in the early days.
— Austin Rief \u2615\ufe0f (@austin_rief) December 5, 2020
Understanding the journey is more important than knowing where they are today.
Fooled by Randomness by @nntaleb: https://t.co/fB9ncIMlvE
Great blog from @ShaneAParrish and @FarnamStreet: https://t.co/o1T85OJMl7
1/ An Allegory of Finance
— Sahil Bloom (@SahilBloom) July 18, 2020
I have been posting a lot of educational (and humorous!) threads on finance, money, and economics.
My mission is simple: to demystify these concepts and make them accessible to everyone.
All of the threads can be found below. Enjoy and please share!
More from Sahil Bloom
Short Squeeze 101
If you follow financial markets (or if you watch Billions), you've heard the phrase "short squeeze" used quite frequently.
But what is a "short squeeze" and how does it work?
Here's Short Squeeze 101!
👇👇👇
1/ First, the basics.
The "short" in "short squeeze" refers to the concept of short selling.
The basics are covered in my thread below.
https://t.co/xecJYNCxMs
TL;DR - short selling is a way of betting against a stock - i.e. betting that its price will decline.
2/ "Short interest" is a measure of how heavily an asset is shorted by the market.
It is the total number of shares that have been sold short (borrowed and sold), but have not yet been covered (bought and returned).
It is usually measured as a % of the # of shares outstanding.
3/ A "short squeeze" occurs when a heavily-shorted asset experiences a rapid upward price movement.
When this happens, short sellers may be forced to close their short positions (i.e. buy the stock and return it to the broker), further accelerating the upward price movement.
4/ Let's look at a simple example to show this in action.
We will use Tesla, one of the most heavily-shorted stocks in the world.
Imagine the stock price is $1,000 per share. This seems crazy. Ricky Rational decides to short the stock at this level.
If you follow financial markets (or if you watch Billions), you've heard the phrase "short squeeze" used quite frequently.
But what is a "short squeeze" and how does it work?
Here's Short Squeeze 101!
👇👇👇
1/ First, the basics.
The "short" in "short squeeze" refers to the concept of short selling.
The basics are covered in my thread below.
https://t.co/xecJYNCxMs
TL;DR - short selling is a way of betting against a stock - i.e. betting that its price will decline.
1/ Short Selling 101
— Sahil Bloom (@SahilBloom) July 6, 2020
With the markets continuing to rally, there has been more talk of \u201cshorting\u201d or \u201cshort selling\u201d stocks.
But what does that mean and how does it work?
Here\u2019s a quick educational primer: Short Selling 101 pic.twitter.com/JTrJmuY7fI
2/ "Short interest" is a measure of how heavily an asset is shorted by the market.
It is the total number of shares that have been sold short (borrowed and sold), but have not yet been covered (bought and returned).
It is usually measured as a % of the # of shares outstanding.
3/ A "short squeeze" occurs when a heavily-shorted asset experiences a rapid upward price movement.
When this happens, short sellers may be forced to close their short positions (i.e. buy the stock and return it to the broker), further accelerating the upward price movement.
4/ Let's look at a simple example to show this in action.
We will use Tesla, one of the most heavily-shorted stocks in the world.
Imagine the stock price is $1,000 per share. This seems crazy. Ricky Rational decides to short the stock at this level.
Shared a lot of wins publicly in 2021, so it feels appropriate to share the losses just as publicly.
Here are my 10 biggest Ls from 2021 (and what I learned from each one):
Dopamine Addiction
Humans were not made for social media—the dopamine hits are dangerous.
I fell victim.
On several occasions, I found myself constantly refreshing my notifications on a viral thread.
It was gross.
I’m learning to physically force separation to avoid it.
Hustle Culture Fail
I spent the better part of the last decade as a hustle culture aficionado.
Then I burned myself out and was totally incapable of thinking creatively.
I made a change. Now I:
• Work like a lion
• Sleep 8 hours
• Take more walks
My life & work have 10Xed.
Solana Fail
I invested in Solana early and was riding high when it hit $30+ in April—10X+ on my investment.
I sold it and thought I was the next Warren Buffett.
Then it hit $100, $200, & $250—as I stubbornly sat on the sidelines refusing to re-enter.
I am not Warren Buffett.
The Hedonic Treadmill
I tweeted this in May—and then failed to practice what I preached.
Every win felt a bit less exciting. It’s part of our biology, but it was no way to live.
Measure internally, not externally.
Here are my 10 biggest Ls from 2021 (and what I learned from each one):
Dopamine Addiction
Humans were not made for social media—the dopamine hits are dangerous.
I fell victim.
On several occasions, I found myself constantly refreshing my notifications on a viral thread.
It was gross.
I’m learning to physically force separation to avoid it.
Hustle Culture Fail
I spent the better part of the last decade as a hustle culture aficionado.
Then I burned myself out and was totally incapable of thinking creatively.
I made a change. Now I:
• Work like a lion
• Sleep 8 hours
• Take more walks
My life & work have 10Xed.
Solana Fail
I invested in Solana early and was riding high when it hit $30+ in April—10X+ on my investment.
I sold it and thought I was the next Warren Buffett.
Then it hit $100, $200, & $250—as I stubbornly sat on the sidelines refusing to re-enter.
I am not Warren Buffett.
The Hedonic Treadmill
I tweeted this in May—and then failed to practice what I preached.
Every win felt a bit less exciting. It’s part of our biology, but it was no way to live.
Measure internally, not externally.
The Hedonic Treadmill is real.
— Sahil Bloom (@SahilBloom) May 21, 2021
Humans have a tendency to quickly return to a baseline level of happiness after positive events.
Step off the treadmill.
Focus on increasing your happiness baseline, not on the height or frequency of the spikes above it.
More from For later read
There is some valuable analysis in this report, but on the defense front this report is deeply flawed. There are other sections of value in report but, candidly, I don't think it helps us think through critical question of Taiwan defense issues in clear & well-grounded way. 1/
Normally as it might seem churlish to be so critical, but @cfr is so high-profile & the co-authors so distinguished I think it’s key to be clear. If not, people - including in Beijing - could get the wrong idea & this report could do real harm if influential on defense issues. 2/
BLUF: The defense discussion in this report does not engage at the depth needed to add to this critical debate. Accordingly conclusions in report are ill-founded - & in key parts harmful/misleading, esp that US shldnt be prepared defend Taiwan directly (alongside own efforts). 3/
The root of the problem is that report doesn't engage w the real debate on TWN defense issues or, frankly, the facts as knowable in public. Perhaps the most direct proof of this: The citations. There is nothing in the citations to @DeptofDefense China Military Power Report...4/
Nor to vast majority of leading informed sources on this like Ochmanek, the @RANDCorporation Scorecard, @CNAS, etc. This is esp salient b/c co-authors by their own admission have v little insight into contemporary military issues. & both last served in govt in Bush 43. 5/
This is an excellent report, and I'm glad to have joined the study group. The central focus on avoiding war is understandable--a US-China war would be catastrophic and should be avoided. But protecting Taiwan's security and prosperity requires doing more. 1/x https://t.co/P0Sg4LJcpV
— Bonnie Glaser / \u845b\u4f86\u5100 (@BonnieGlaser) February 12, 2021
Normally as it might seem churlish to be so critical, but @cfr is so high-profile & the co-authors so distinguished I think it’s key to be clear. If not, people - including in Beijing - could get the wrong idea & this report could do real harm if influential on defense issues. 2/
BLUF: The defense discussion in this report does not engage at the depth needed to add to this critical debate. Accordingly conclusions in report are ill-founded - & in key parts harmful/misleading, esp that US shldnt be prepared defend Taiwan directly (alongside own efforts). 3/
The root of the problem is that report doesn't engage w the real debate on TWN defense issues or, frankly, the facts as knowable in public. Perhaps the most direct proof of this: The citations. There is nothing in the citations to @DeptofDefense China Military Power Report...4/
Nor to vast majority of leading informed sources on this like Ochmanek, the @RANDCorporation Scorecard, @CNAS, etc. This is esp salient b/c co-authors by their own admission have v little insight into contemporary military issues. & both last served in govt in Bush 43. 5/
You May Also Like
1/12
RT-PCR corona (test) scam
Symptomatic people are tested for one and only one respiratory virus. This means that other acute respiratory infections are reclassified as
2/12
It is tested exquisitely with a hypersensitive non-specific RT-PCR test / Ct >35 (>30 is nonsense, >35 is madness), without considering Ct and clinical context. This means that more acute respiratory infections are reclassified as
3/12
The Drosten RT-PCR test is fabricated in a way that each country and laboratory perform it differently at too high Ct and that the high rate of false positives increases massively due to cross-reaction with other (corona) viruses in the "flu
4/12
Even asymptomatic, previously called healthy, people are tested (en masse) in this way, although there is no epidemiologically relevant asymptomatic transmission. This means that even healthy people are declared as COVID
5/12
Deaths within 28 days after a positive RT-PCR test from whatever cause are designated as deaths WITH COVID. This means that other causes of death are reclassified as
RT-PCR corona (test) scam
Symptomatic people are tested for one and only one respiratory virus. This means that other acute respiratory infections are reclassified as
4/10
— Dr. Thomas Binder, MD (@Thomas_Binder) October 22, 2020
...indication, first of all that testing for a (single) respiratory virus is done outside of surveillance systems or need for specific therapy, but even so the lack of consideration of Ct, symptoms and clinical findings when interpreting its result. https://t.co/gHH6kwRdZG
2/12
It is tested exquisitely with a hypersensitive non-specific RT-PCR test / Ct >35 (>30 is nonsense, >35 is madness), without considering Ct and clinical context. This means that more acute respiratory infections are reclassified as
6/10
— Dr. Thomas Binder, MD (@Thomas_Binder) October 22, 2020
The neither validated nor standardised hypersensitive RT-PCR test / Ct 35-45 for SARS-CoV-2 is abused to mislabel (also) other diseases, especially influenza, as COVID-19.https://t.co/AkFIfTCTkS
3/12
The Drosten RT-PCR test is fabricated in a way that each country and laboratory perform it differently at too high Ct and that the high rate of false positives increases massively due to cross-reaction with other (corona) viruses in the "flu
External peer review of the RTPCR test to detect SARS-CoV-2 reveals 10 major scientific flaws at the molecular and methodological level: consequences for false positive results.https://t.co/mbNY8bdw1p pic.twitter.com/OQBD4grMth
— Dr. Thomas Binder, MD (@Thomas_Binder) November 29, 2020
4/12
Even asymptomatic, previously called healthy, people are tested (en masse) in this way, although there is no epidemiologically relevant asymptomatic transmission. This means that even healthy people are declared as COVID
Thread web\u2b06\ufe0f\u2b07\ufe0f
— Dr. Thomas Binder, MD (@Thomas_Binder) December 16, 2020
The fabrication of the "asymptomatic (super) spreader" is the coronation of the total nons(ci)ense in the belief system of #CoronasWitnesses.
Asymptomatic transmission 0.7%; 95% CI 0%-4.9% - could well be 0%!https://t.co/VeZTzxXfvT
5/12
Deaths within 28 days after a positive RT-PCR test from whatever cause are designated as deaths WITH COVID. This means that other causes of death are reclassified as
8/8
— Dr. Thomas Binder, MD (@Thomas_Binder) March 24, 2020
By the way, who the f*** created this obviously (almost) worldwide definition of #CoronaDeath?
This is not only medical malpractice, this is utterly insane!https://t.co/FFsTx4L2mw
