COVID-19/Coronavirus Information and Support Thread (see OP for useful links)

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The RT-PCR test has a specificity of 95% and a sensitivity of 95%. Given that negative tests outweigh positive ones 50 times over, the number of false negatives is thus likely to be 50 times higher than the number of false positives. Sure, you can wave away five positives out of every 100, but there's another 250 unknown positives hiding away.

That's the wrong way round, as I've suggested twice before. Now that I've gone off and checked three times, I'm getting pretty confident of that!

The false positive rate is the proportion of all negatives that still yield positive test outcomes
https://en.wikipedia.org/wiki/False...tives#False_positive_and_false_negative_rates

So - if FPR and FNR can be applied in this way, which I'm really not sure about - false positives would be 50 times higher than false negatives for your example, and only 0.1 unknown positives hiding away.

I doubt, when we are at the edge of the range, that doing such calcs gives us anything valid or useful. For one thing, we get a number via FPR that is much higher than the rate of positive test results seen during July.

Anyway, as I showed earlier, factoring in false positives to the test results actually makes the recent rise more extreme than otherwise, even when allowing for increased testing.
 
That's the wrong way round, as I've suggested twice before. Now that I've gone off and checked three times, I'm getting pretty confident of that!
I didn't use that term, because it apparently is easily mutable:
The RT-PCR test has a specificity of 95% and a sensitivity of 95%. Given that negative tests outweigh positive ones 50 times over, the number of false negatives is thus likely to be 50 times higher than the number of false positives. Sure, you can wave away five positives out of every 100, but there's another 250 unknown positives hiding away.
I used the terms specificity and sensitivity, which are, according to the paper everyone's referring to now, 95% apiece for the RT-PCR test (I don't know if that's true but it seems fair; my test, for circulating tumour cells, was also RT-PCR and 98% sensitive and 96% specific).

That means that 5% of tested positives are falsely positive, and 5% of tested negatives are falsely negative. Only ~2% of tests give a positive result, so negative tests outweigh positive tests by 49:1, and so will false negatives to false positives.

I really think you've got this wrong. @Famine
giphy.gif
 
Check out the bmj link and see if you can fudge the numbers to get more false negatives than positives. You can't. Edit (You can, but the numbers are ridiculous)

That means that 5% of tested positives are falsely positive, and 5% of tested negatives are falsely negative. Only ~2% of tests give a positive result, so negative tests outweigh positive tests by 49:1, and so will false negatives to false positives.

Using a pretest probability of 10% chance that I am predisposed to your tumour cells 98/96

10 true positives 4 false positives 86 true negatives 0 false negatives.

So I don't see where you are getting your numbers from.

https://www.bmj.com/content/369/bmj.m1808

If you get more false negatives than false positives, then the test is not worth doing.
 
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Check out the bmj link and see if you can fudge the numbers to get more false negatives than positives. You can't. Edit (You can, but the numbers are ridiculous)

As best I can tell, nobody said that.

If you get more false negatives than false positives, then the test is not worth doing.

What?

BTW, every time I click your link it shows more false negatives than false positives.
 
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Using a pretest probability of 10% chance that I am predisposed to your tumour cells 98/96

10 true positives 4 false positives 86 true negatives 0 false negatives.
It looks like you're predisposed to missing words out, because I can't make top nor bottom of that. Could you clarify with some extra words, perhaps structural ones?

In addition, you'd need to have colon cancer already for the CTC test (it's a tool for outcome, not for diagnosis), so let's hope you don't need it, eh?

If you get more false negatives than false positives, then the test is not worth doing.
Why?
 
Since we've gone back to the month old argument of "look at the deaths", here's a reminder that a 99% chance of surviving Covid doesn't guarantee you actually recover from it without issue.
Mayo Clinic
Most people who have coronavirus disease 2019 (COVID-19) recover completely within a few weeks. But some people — even those who had mild versions of the disease — continue to experience symptoms after their initial recovery.

Older people and people with many serious medical conditions are the most likely to experience lingering COVID-19 symptoms.

Organs that may be affected by COVID-19 include:
  • Heart. Imaging tests taken months after recovery from COVID-19 have shown lasting damage to the heart muscle, even in people who experienced only mild COVID-19 symptoms. This may increase the risk of heart failure or other heart complications in the future.
  • Lungs. The type of pneumonia often associated with COVID-19 can cause long-standing damage to the tiny air sacs (alveoli) in the lungs. The resulting scar tissue can lead to long-term breathing problems.
  • Brain. Even in young people, COVID-19 can cause strokes, seizures and Guillain-Barre syndrome — a condition that causes temporary paralysis. COVID-19 may also increase the risk of developing Parkinson's disease and Alzheimer's disease.
It's important to remember that most people who have COVID-19 recover quickly. But the potentially long-lasting problems from COVID-19 make it even more important to reduce the spread of the disease by following precautions such as wearing masks, avoiding crowds and keeping hands clean.
https://www.mayoclinic.org/diseases...th/coronavirus-long-term-effects/art-20490351

Hackensack Meridian Health
For some who recover from COVID-19, symptoms like fatigue, shortness of breath, muscle pain, confusion, headaches and even hallucinations are among the growing number of issues survivors face following the illness.

“Individuals recovering from COVID-19 may struggle with a number of respiratory, cardiac and kidney problems,” warns Laurie Jacobs, M.D., chair of the Department of Internal Medicine at Hackensack University Medical Center. “They also have an increased risk of blood clots, which can potentially lead to a stroke or heart attack.”
https://www.hackensackmeridianhealt...9/what-are-the-long-term-effects-of-covid-19/

Science Mag
Her early symptoms were textbook for COVID-19: a fever and cough, followed by shortness of breath, chest pain, and extreme fatigue. For weeks, she struggled to heal at home. But rather than ebb with time, Akrami’s symptoms waxed and waned without ever going away. She’s had just 3 weeks since March when her body temperature was normal.

“Everybody talks about a binary situation, you either get it mild and recover quickly, or you get really sick and wind up in the ICU,” says Akrami, who falls into neither category. Thousands echo her story in online COVID-19 support groups. Outpatient clinics for survivors are springing up, and some are already overburdened. Akrami has been waiting more than 4 weeks to be seen at one of them, despite a referral from her general practitioner.

The list of lingering maladies from COVID-19 is longer and more varied than most doctors could have imagined. Ongoing problems include fatigue, a racing heartbeat, shortness of breath, achy joints, foggy thinking, a persistent loss of sense of smell, and damage to the heart, lungs, kidneys, and brain.
https://www.sciencemag.org/news/202...ovid-19-s-lingering-problems-alarm-scientists

170k people die from heart disease every year. We don't ban all fatty foods, sugar, alcohol and cigarettes. We accept it as a sad part of life.
This is an old, irrelevant argument made to attempt justifying the death toll as "normal". Except heart disease is not contagious. Covid is, and in the US, is already reported as the 3rd leading cause of death. If we want to continue politicizing it, I'm sure America would love to make it the leading cause of death & be #1 in another Covid-related category.
"COVID is now the No. 3 cause of death in the U.S. -- ahead of accidents, injuries, lung disease, diabetes, Alzheimer's, and many, many other causes," Frieden said.

The CDC says heart disease and cancer are the first- and second-leading causes of death.
https://www.webmd.com/lung/news/20200818/covid-the-third-leading-cause-of-death-in-the-us
She's far more likely to be asymptomatic (80% of cases according to WHO) or one of the massive number of tests that are false positive.
Asymptomatic doesn't mean you're safe. You still spread it, and you're still susceptible to the effects of it.
“They are seeing there is damage to the lungs in these asymptomatic children. ... We don’t know how that is going to manifest a year from now or 2 years from now,” Alonso told Palm Beach County commissioners at a July meeting. “Is that child going to have chronic pulmonary problems or not?”

Valentina Puntmann, MD, has wondered about long-term consequences of COVID-19 on the heart. Puntmann is an expert in heart imaging at the University Hospital Frankfurt in Germany. She and a team of researchers recently scanned the hearts of 100 patients who had recently recovered from COVID-19, including 18 who were asymptomatic. They found that 78 had signs of heart damage, including elevated levels of troponin, proteins released by the heart muscle when it is damaged. Not all of the asymptomatic patients had markers for heart damage, but a few who did had some of the highest levels measured in the study.
https://www.webmd.com/lung/news/20200811/asymptomatic-covid-silent-but-maybe-not-harmless

This virus is clearly still too new to pinpoint what the lingering effects will do down the road (though the fact they're there is obviously concerning the medical community), or who is most likely to develop them b/c the research I've read seems to indicate a wide board of survivor demographics are all at risk to lingering effects whether you're young or old, asymptomatic or not, have mild or severe cases.
 
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Put numbers into the BMJ link and the numbers you get out show that you get 4 false positives and 0 false negatives.

Why would a test be rubbish if it has more false negatives than positives? Hmmmm. MAybe it's because the point of a test is to determine if someone has a disease. If there are more false negatives then you are letting a lot of people ill, whilst they have been tested negative. Much better to have more false positives, I'm sure you'll agree.
 
Put numbers into the BMJ link and the numbers you get out show that you get 4 false positives and 0 false negatives.

Why would I do that?

Why would a test be rubbish if it has more false negatives than positives? Hmmmm. MAybe it's because the point of a test is to determine if someone has a disease. If there are more false negatives then you are letting a lot of people ill, whilst they have been tested negative. Much better to have more false positives, I'm sure you'll agree.

But.... why does it make it "rubbish"?
 
I didn't use that term, because it apparently is easily mutable:

You didn't there, but you said before:
"False positive rate" (or ratio) is simply the inverse of sensitivity (and false negative rate is the inverse of specificity).

which has sensitivity and specificity swapped over, AIUI, and is what you use here:

I used the terms specificity and sensitivity, which are, according to the paper everyone's referring to now, 95% apiece for the RT-PCR test (I don't know if that's true but it seems fair; my test, for circulating tumour cells, was also RT-PCR and 98% sensitive and 96% specific).

That means that 5% of tested positives are falsely positive, and 5% of tested negatives are falsely negative. Only ~2% of tests give a positive result, so negative tests outweigh positive tests by 49:1, and so will false negatives to false positives.

I believe it means that:

From sensitivity, 95% of true positives will have a positive test result, with the other 5% having an incorrect negative result.
So 5% of 2% are false negative results.

From specificity, 95% of true negatives will have a negative test result, with the other 5% having an incorrect positive result.
So 5% of 98% are false positive results.

So false positives outweigh false negatives by 49:1.

(also note this assumes that 2% is the prevalence of true positives, not that 2% of results are positive)
 
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MAybe it's because the point of a test is to determine if someone has a disease. If there are more false negatives then you are letting a lot of people ill, whilst they have been tested negative. Much better to have more false positives, I'm sure you'll agree.
If everyone's test results were for some reason secret that might be true. It ignores the need for gathering data.
 
Why would I do that?
I accept that you just pressed the link. But put Famines numbers in and you'll see what I mean.

But.... why does it make it "rubbish"?

"If you have patients coming into hospital and you're going to put them into what has been determined to be a COVID-free ward, you have to have the most sensitive test available," Procop says. "Because once you put somebody with COVID into a COVID-free ward, it's no longer a COVID-free [ward] any more. It's your new COVID ward."

You won't put them in the ward if you have a false positive. You could if they had a false negative. That's why tests need to have a high sensitivity (over 95%).

"A high rate of false negatives would definitely be cause for concern," says Dr. Thomas Inglesby, who runs the Center for Health Security at the Johns Hopkins School of Public Health.

https://www.npr.org/sections/health...ives-from-quick-covid-19-test?t=1600799597252
 
WTF? Numbers is numbers. Secrets? This is about statistics.
That's exactly what I'm saying.

Why would a test be rubbish if it has more false negatives than positives? Hmmmm. MAybe it's because the point of a test is to determine if someone has a disease. If there are more false negatives then you are letting a lot of people ill, whilst they have been tested negative. Much better to have more false positives, I'm sure you'll agree.
You described the point of the disease testing from a view that ignores the need for statistics.
A statistical analysis should have as much data as possible to work with for it to make the most accurate determinations. Which means the point of testing goes a lot further than determining if somebody is ill. Of course some of the data will be from false results but we need to collect that too in order to learn about it.

Maybe either more false positives or negatives would be better, I haven't thought about that in depth. I wasn't specifically talking about that part.

Edit: See the bolded correction above. Sorry, that didn't make sense the way I originally typed it.
 
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I accept that you just pressed the link. But put Famines numbers in and you'll see what I mean.

Did he post a pre-test probability?

"If you have patients coming into hospital and you're going to put them into what has been determined to be a COVID-free ward, you have to have the most sensitive test available," Procop says. "Because once you put somebody with COVID into a COVID-free ward, it's no longer a COVID-free [ward] any more. It's your new COVID ward."

You won't put them in the ward if you have a false positive. You could if they had a false negative. That's why tests need to have a high sensitivity (over 95%).

"A high rate of false negatives would definitely be cause for concern," says Dr. Thomas Inglesby, who runs the Center for Health Security at the Johns Hopkins School of Public Health.

https://www.npr.org/sections/health...ives-from-quick-covid-19-test?t=1600799597252

But why does that make it "rubbish"? I get why you'd prefer a more accurate test.
 
I can't see what you might have missed, but I got his screenshot with those values.

Quite an interesting gadget to play around with.

Hmmm... I closed the tab and reloaded it and now I get his numbers too. Something screwy with how it loaded before.

(My previous screenshot still looks right, just not that last one)


Edit:

Ok so I took another crack at the (potentially flaky) website indicating statistical output. For the numbers here:
https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html#:~:text=The sensitivity of rapid antigen,of detection of the test.

Sensitivity ~90% and Specificity ~100% (I put 99%), there are no false positives in a population of 100 (seems like there should be 1) and the number of false negatives goes up with pre-test likelihood.

For the numbers here:

https://www.cdc.gov/coronavirus/201...dy-tests-guidelines.html#anchor_1590264273029

The suggested sensitivity 90% is with specificity of 99.5% or greater gives you the same results.

So... lots of false negatives compared to false positives.
 
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I've no idea what to put in the "pre-test probability" box for an individual test either. Let's say I've spent a hour at a table with someone who shortly after falls ill, but I don't have any symptoms yet - would a GP put 20%? 50%? 90%?

It does actually work to enter into that box an estimate of the true prevalence of covid, and see the results as if they were from a randomised trial. However, given that in this case we're looking at a small %, it only covers 100 people, and it rounds everything to integers, the numbers (particularly zeroes) it comes up with are a bit misleading.

covid-test-calc.png


Further down that page I see they estimate a sensitivity of only 70%, so I tried that too...
(the page was published 12 May 2020, so 70% could well be out of date).

covid-test-calc-70.png


Seems legit to me, reducing sensitivity moves results from true positive to false negative. Leaves false positives unchanged.
 
I've no idea what to put in the "pre-test probability" box for an individual test either. Let's say I've spent a hour at a table with someone who shortly after falls ill, but I don't have any symptoms yet - would a GP put 20%? 50%? 90%?

It does actually work to enter into that box an estimate of the true prevalence of covid, and see the results as if they were from a randomised trial.

That's what I started doing, just treat the pre-test probability as the portion of the population. So if I want to see more positives, I bump the pre-test probability.
 
If anyone was curious about some of the vaccine tests being done, here's a couple Dallasites who detailed the process so far for them with the Pfizer Covid trial underway. Pretty similar symptoms, guessing the side effects are a result of any amount of Covid being introduced to create antibodies?
Got the trial vaccine after volunteering for it: got two shots separated by three weeks period and it was ... interesting. Went to Baylor and nasal swab was done, they drew two vials of blood and shot me up with the vaccine. The first day after the first shot was not comfortable, shoulder was hurting, I had a fuzzy head, a mild headache and general fatigue. Headache went away the next day as did the fatigue but my shoulder still hurt the next day. Third day after the shot I was back to 100%.

Second shot hit me harder, shoulder was hurting even more, I had chills but no fever and general fatigue lasted for a day.

Then, I went to get a serological antibody test on my own, three weeks after the first shot and voila - they found a "ton" of Covid antibodies in my blood so I am pretty much close to being immune. I will keep masking up as I do not want to test the fate, lol.
I volunteered for the pfizer trial as well and had my second dose last week. Pretty sure I got the vaccine. I had some fatigue a few hours after my first dose and arm pain for 3 days I couldn’t sleep on it the first night. After the second dose I had the same arm pain (different arm) for 3 days, fatigue, sweats/chills for first two nights, a 99.3 temp on the second night, and fuzzy head for 3 days which overall I thought the fuzzy head seemed to be the most annoying symptom. No headache for me. Symptoms fully cleared after 3 days. I took Tylenol everyday. I think i’ll go get an antibody test late this week that should be enough time as Pfizer says they’re interim report will only include covid positives starting 10 days after second dose which leads me to believe that is about how long it takes to develop enough antibodies to be protected.
The first guy added they will be tested all the way through 2022 through blood samples, and the first part of the study will be looking at how long the antibodies last.
 
If anyone was curious about some of the vaccine tests being done, here's a couple Dallasites who detailed the process so far for them with the Pfizer Covid trial underway. Pretty similar symptoms, guessing the side effects are a result of any amount of Covid being introduced to create antibodies?

The first guy added they will be tested all the way to 2022 through blood samples, and the first part of the study will be looking at how long the antibodies last.

Yup, those are all pretty standard side effects when you get a vaccine. I just don't think we really give it much thought since most of our vaccines are done when we are young kids. But I do know that you can experience fever, soreness, chills, and a whole host of other things even with the yearly flu shot. My wife almost always feels like crap for a day or two after getting it.

The good news is we're not hearing about any prevalent serious side effects. I know one thing researchers are often worried about is seizures or anaphylaxis from vaccines because that can happen. I'm sure some people will have a poor reaction to a COVID vaccine, but as long as it's fairly rare, it shouldn't be much of a worry. I'm not sure what the serum will be made up for the COVID vaccine either, only that it requires to be stored in sub-zero conditions (the Pfizer one anyway). My guess is there will be some people that will have a reaction to that as well, kind of like how with the flu vaccine you can't take certain ones if you're allergic to eggs.

I really wish I could get in on the trial. I think I've signed up for a couple different ones now. I'd be more than willing to feel like garbage for a couple of days if it meant I wouldn't have to worry about COVID.
 
I really wish I could get in on the trial. I think I've signed up for a couple different ones now. I'd be more than willing to feel like garbage for a couple of days if it meant I wouldn't have to worry about COVID.

Assuming you have no other contributing factor(s) that CV19 would impact, why would you take the risk of taking a vaccine with no understanding of any medium or long term side effects... and no recourse to the manufacturer if those side effects are life limiting.

According to your profile you're 33 years old.

In The UK there are 13m people aged 20-34.

Year to date, 157 have CV19 listed as a cause of death... including those with contributing a factor(s)

1 in 82,000

Though given only 307 people under the age of 65 have died from Covid in the UK with no other contributing factor(s), you're chances at 33 years old will be significantly better than that if you are otherwise healthy.

Even ignoring contributing factors, in the UK you have around the same chance of getting murdered as you do of dying of CV19 if you're 20-34... I would expect your chances of getting murdered in the US will be a lot higher given murder rates per capita are c.4x than the UK.

3 x more 20-34 year olds die in 'transport accidents'
5 x more die of 'accidental poisoning'

Why are you worrying about catching Covid?
 
Assuming you have no other contributing factor(s) that CV19 would impact, why would you take the risk of taking a vaccine with no understanding of any medium or long term side effects... and no recourse to the manufacturer if those side effects are life limiting.

According to your profile you're 33 years old.

In The UK there are 13m people aged 20-34.

Year to date, 157 have CV19 listed as a cause of death... including those with contributing a factor(s)

1 in 82,000

Though given only 307 people under the age of 65 have died from Covid in the UK with no other contributing factor(s), you're chances at 33 years old will be significantly better than that if you are otherwise healthy.

Even ignoring contributing factors, in the UK you have around the same chance of getting murdered as you do of dying of CV19 if you're 20-34... I would expect your chances of getting murdered in the US will be a lot higher given murder rates per capita are c.4x than the UK.

3 x more 20-34 year olds die in 'transport accidents'
5 x more die of 'accidental poisoning'

Why are you worrying about catching Covid?
Death isn't the only serious effect from Covid. But apart from the risk of dying there is also the risk of giving other people a disease they die from, possible relatives.
And if everyone thought like you there is no point in vaccination. In order to work the majority of the population is to have the vaccination....
 
Death isn't the only serious effect from Covid. But apart from the risk of dying there is also the risk of giving other people a disease they die from, possible relatives.
And if everyone thought like you there is no point in vaccination. In order to work the majority of the population is to have the vaccination....

Options 1: Risk catching CV19, a virus that I'm 80% likely not to even know I've had, which is similar to bad case of flu in vast the majority of full infections in healthy people, with a potentially (if at all, time will tell) tiny chance of suffering from long term effects and an infinitesimally small chance of dying from.

Option 2: Risk having a vaccine that's been knocked up in 6 months, under massive political pressure and with unknown medium/long term side effects.

I don't think I'll be front of the queue for option 2.

I've had the usual vaccinations... ones that have been thoroughly tested, and have been proven to be safe over multiple generations.

If I was 65 years old the risk/benefit decision might be different.

Your profile indicates your Swedish... a country that has taken a much more balanced approach to Covid.
 
Options 1: Risk catching CV19, a virus that I'm 80% likely not to even know I've had, which is similar to bad case of flu in vast the majority of full infections in healthy people, with a potentially (if at all, time will tell) tiny chance of suffering from long term effects and an infinitesimally small chance of dying from.

Option 2: Risk having a vaccine that's been knocked up in 6 months, under massive political pressure and with unknown medium/long term side effects.

I don't think I'll be front of the queue for option 2.

I've had the usual vaccinations... ones that have been thoroughly tested, and have been proven to be safe over multiple generations.

If I was 65 years old the risk/benefit decision might be different.

Your profile indicates your Swedish... a country that has taken a much more balanced approach to Covid.
I am. And our approach hasn't been all that different. And if the young ones doesn't vaccinate the people who can not use vaccination will be unprotected.
 
I wonder if we should change COVID deaths to represent not that the disease has a 5% chance of killing you, but rather that every single time you walk around ignoring public safety guidelines, you run a 5% chance of a madman coming and slitting your throat. It might help get the message across.

I've basically given up hope in one grocery store I sparingly go to (and now even less). People keep walking around with their noses uncovered (how about a PSA by WHO/CDC/anyone with a brain on how to use a mask? Apparently it's really hard!), eating/drinking food (usually not an issue during non-pandemic times, but pretty sure they will forget to cover their face between bites/sips), and talking on the phone with no mask on. Heck, it might even make sense to ban the people who walk in without a mask (I saw two of them as I was leaving, one of them AN ACTUAL EMPLOYEE) from ever entering the store again, or firing employees who don't comply.
 
I wonder if we should change COVID deaths to represent not that the disease has a 5% chance of killing you, but rather that every single time you walk around ignoring public safety guidelines, you run a 5% chance of a madman coming and slitting your throat. It might help get the message across.

67520966.jpg


If trolling, then have a couple of :lol::lol: from me.

If serious, you're on the same level of bat**** crazy as the people who believe '5G causes Covid'.

Either way, the most entertaining Coivd post I've seen for a while :lol:
 
Assuming you have no other contributing factor(s) that CV19 would impact, why would you take the risk of taking a vaccine with no understanding of any medium or long term side effects... and no recourse to the manufacturer if those side effects are life limiting.

Vaccines have been around.


In The UK there are 13m people aged 20-34.

Year to date, 157 have CV19 listed as a cause of death... including those with contributing a factor(s)

Bump your numbers to include serious side effects, then take a step back, look at it, and understand that that number is despite all of the best possible efforts to contain this thing.

Even ignoring contributing factors, in the UK you have around the same chance of getting murdered as you do of dying of CV19 if you're 20-34...

Think about what you just said for a second. Your chances of being murdered are equivalent to getting killed by a disease that the entire world has turned itself upside down to stop. All of our efforts, social distancing, lockdowns, masks, hand santizing, temp checks, constant PSAs, closing bars and restaurants, closing schools, all of it... to get COVID down to the ambient level of murder for one of the best age demographics.

Now imagine we stopped "worrying" about it.

And that's just from a purely selfish perspective. It completely ignores your chances of killing the elderly people around you.
 
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