Saturday, September 19, 2020

Can we avoid lockdown?

I considered briefly the magnitude of the response needed to address the COVID-19 pandemic, and concluded that - roughly - a factor of 10 reduction in social activity was required.

The question then becomes - how to achieve that?

Clearly, lockdown works (although the fact that our decline was slower than it should have been indicates that it wasn't working optimally - lacklustre leadership, being two weeks late into lockdown, and a significant selfish minority who clearly thought the restrictions weren't for them, contributed in part.

There are massive negative economic and societal consequences of lockdown, so it would be better to avoid it if you can. Can we?

What are the options?

  • Working from home: this dramatically eliminates both the work contact and public transport contact elements. It's a sufficiently large component that if you don't do it, you can't win. So, where possible, people should work from home. There's still going to be a set of people for whom this isn't possible.
  • Avoid public transport: yes, this helps a bit, but has negative impacts. Remember, we have a climate disaster looming on the horizon. If the majority work from home, then that reduces the occupancy - and thus the risk - for those that need to travel.
  • Eliminate large-scale events: the sheer number of people, and their closeness, surely indicates that live theatre, sport, concerts, and the like, simply can't be contemplated for a while.
  • Rethink large-scale events: large scale events have a couple of problems, first you're putting a huge number of people in direct contact at the event, and you're having a lot of mixing on the way in and out (and many will visit other social venues as part of the event, making things even worse). But if you only had isolated boxes - and many venues already have some provision like this, after all - with no way for people in different boxes to mix, then you can get to a point where it's not really any worse then the groups meeting to watch the event on TV in a bar or at home.
  • Shut down bars and restaurants: there's a massive economic and social hit from this. This is a smaller version of the question about avoiding total lockdown.
  • Rethink bars and restaurants: how far can you eliminate the risk by having isolated groups (bubbles), table service only, one way routes, and ramping up the restrictions? I think you can actually go a long way from the norm. Having visited a few bars and restaurants, most are doing a pretty good job. The fundamental problem again is those in the selfish subclass who won't obey the restrictions and ruin things for everyone. You're going to have massively reduced occupancy (simply by spacing people out) which reduces the risk. Which also reduces the risk because the reduction in capacity means people won't be able to go out as often.
  • Testing: if you test everyone continuously, and just barricade the infected, then you should allow everyone else to get back to normal, right? Not so fast. The point here is that a single negative test doesn't mean anything. Worse, any contact means you need to get retested - over and over. That's the sort of thing you have to do in hospitals, it's simply not feasible to cover the whole population at the required density.
  • Early closing: I've seen the suggestion that bars should close early. I'm not at all sure that this will help much, as it just pushes people into packing more densely into the hours that places are opening. If anything, you want to expand opening hours (presumably early opening) to spread customers out as much as possible. The only way I can see this helping is if it discourages people from going out at all.
  • Ban pub crawls: this seems to me like a no-brainer, to be honest. Restricting people to a single venue massively reduces the mixing effect. (And it seems likely that there's a strong correlation between pub-crawlers and selfish superspreaders.)
  • Track and trace: essential, but only works if you massively reduce your interactions in the first place. If you try and carry on as normal, then everyone ends up potentially coming into contact with an infected person and you have to lock everybody away as a result.
  • Social distancing: taken as a given, but not enough alone unless you push it well beyond 2 metres. Doesn't matter how far apart you are if you have to share the same door handle, though.
  • Face coverings: again, unlikely to be enough on its own. Really, you should be thinking about face coverings, social distancing, and similar precautions as being an extra level of protection if you can't avoid an activity at all (such as shopping for groceries). You shouldn't take face coverings as an excuse to enable you to partake in riskier activities.
  • Redefined infrastructure: take the things that we have to do and eliminate risk. Examples include automatic doors (you don't touch anything that someone else has), foot or knee operated taps rather than turning by hand. Individual lifts, and likewise travel compartments rather than massive open carriages.
There's no silver bullet here. Saying "if we all just did X" won't work, no single action is enough. This has to be a concerted attempt, all the options need to be pursued together.
 
I think we could avoid lockdown, but it requires a huge amount of work. You need to go fo the big hitters - working from home as much as conceivably possible, scrapping all large events entirely. Then you need to layer on every single measure and precaution you can. And you need a high level of adherence to make it work.

Sadly, we have a government that hasn't the gumption to do the big things or the eye for detail to do all the little things, and the great british public has far too many gormless prats to expect the measures necessary will be followed.

Friday, September 18, 2020

The accuracy of COVID-19 statistics

Nobody really knows how many people have died in the UK due to COVID-19. There are currently 3 numbers that might give a bit of a clue:

  • The daily statistic of those who've died after a positive test
  • The number who have had COVID-19 mentioned on the death certificate
  • The excess deaths reported compared to a normal year

The last one is more amenable to statistical analysis, but is also subject to a variety of errors: the baseline varies from year to year, and lockdown may increase some types of deaths, while decreasing others (for the latter, consider the reduction in pollution). Still, it's a reasonably well defined number.

The second one is highly tricky, because - absent lots of tests and post-mortems, it's sometimes going to be tricky apportioning the cause of death.

The first one has attracted a lot of attention, and it's the headline number you see in the news. It has the advantage that it's quite well defined (you know, definitively, who has had a test, the outcome, and whether they died). The disadvantage is that it doesn't give you any clue as to whether COVID-19 was actually the cause of death or not - perhaps they got run over by a bus.

Early on, this didn't make much difference. But, over time, the probability that someone would die from another cause obviously increases. So, early in August, the statistic was changed to add a 28-day cut off.

The idea of a cut off is that, very roughly, the number of people who die from COVID-19 after the cut off are offset by those who die of other causes before the cut off. At a nigh level, it makes sense, because otherwise it's going to be wrong, and the error will increase over time.

The question really is whether the correction applied is correct. After all, that 28 days is basically a guess - it's commonly used, so is reasonable for comparison purposes, but it's still a guess.

There are a couple of ways to see if the value for the cut off is reasonable. And for that, we need data. It turns out that we can download the time series from the portal, and have a look at the numbers.

One fortunate thing we have is that the dataset actually includes 3 numbers - raw numbers, with the 28-day cut off, and with a 60-day cut off. As of today, the 28-day cut off removes 6,634 deaths from the starting 44,115, and the 60-day cut off less that half that at 2,695. These are what would come in as deaths from other causes.

First, given the number of positive tests, does that correction look sensible. We know, roughly, that there were ~300,000 positive tests in the first peak. So that's mostly 4-5 months ago. For the 28 day cutoff, that gives a regular remaining life expectancy of 15-19 years to account for the observed deaths. For 60 days, the range is 37-46 years.

The problem with this is that we don't know the demographics of those tested. However (you can look these things up in actuarial tables), for the 28-day number to be accurate, those tested have to be quite old - over 65, whereas the 60 day number would be right for a population of working age - say typically in their 40s. Given that we know that there was little testing in nursing homes, the 28-day life expectancy looks a bit wrong, whereas the 60-day version looks reasonable if you're testing a lot of health workers. It's not definitive, but there's a hint that 28 days is overcorrecting.

Another thing to do is look at the rate of corrected deaths over time. This is what it looks like for 28 days:

and this is for the 60 day data:



There's quite a difference there. Note that our expectation is that the probablity of death from other causes is constant (approximately) over time, so that the overall rate will increase over time (it's constant if there's just a single input at a fixed point in time, but we're testing more people as time goes on so the population is growing - the relatively recent big spike in positive tests hasn't worked its way into the data yet).

From this point of view, the 28-day graph looks a little suspect - it starts to rise 28 days after significant testing, but after day 90 there's a decline. That's plain wrong, indicating that there's a correlation with the time of the test (there are a lot of positive tests in days 30-90 which is when the big first peak was). If they're correlated with the positive test, there's going to be some element of correlation with the cause of the test - namely COVID-19 itself.

By contrast, the 60-day chart has the right shape. The problem is that any large cut off will have the right shape, so it's not telling us anything about the correct number to cut the data at, just that 60 days is beyond it.

The thing is, if you had all the data (inclduing demographics) you could do this properly, and work out what the optimal cut off to minimize errors should be. I just haven't seen that yet. But I'm fairly sure that, while the original quoted numbers overestimated the number of deaths, the new numbers with a 28-day cut off are underestimating the true impact, and they might even be more in error the other way than the original figures were.

Sunday, September 13, 2020

What level of response to Covid-19 do we need?

Short version: quite a lot.

The long version below is a rough attempt for me (a former scientist) to understand the problem and the rough nature of possible solutions.

It starts with the R factor - essentially the number of people that an infectious person passes the disease on to. The more people you infect, the faster the disease grows. If you manage to get to a situation where people infect less than 1 person on average, the disease will decline.

I've seen R factors for the UK of round about 3 in the early stages. That's the effective R factor - even then, before our governmenat finally bothered with a form of lockdown, a significant number of individuals and organisations were taking preventive measures. So the intrinsic R factor could be a bit higher, although 6-9 is the highest range I've seen.

As we've seen, the effective R factor depends on reactive measures and behaviour. So what sort of measures are necessary to get R below 1?

Reember, R is the number of people who can pass the disease on to. So you need to reduce that number from anything between 3 and 9 to below 1. Actually, you need to go a decent way beyond that to give yourself a margin of error. So I'm going to say that you need to reduce the likelihood of passing the infection of by a factor of 10, which basically means reducing direct contact by a factor of 10.

And reducing transmission by a number that large is quite a challenge. If you just carried on and tried to use face coverings and social distansing, I don't think you can get there - they might give you a factor of 2 or 3, which isn't enough.

What level of contact do people have with others? I'm going to try and estimate the number of person-hours of contact you generate in a week. Remember, this is before the pandemic.

  • Work, you might have 40 hours a week in an office or building with 25 people, giving 1,000 contact-hours
  • Commute, You might have 10 hours (1 hour per journey), but cross the paths of 100 people, giving another 1,000 contact-hours
  • Play, a restaurant or bar might be 100 people or so for a couple of hours, but you have to get there and back, and might do it several times a week. And I'm ignoring massive events like theatre, gigs, festivals, sports. So that could be another 1,000 contact-hours

That gives 3,000 contact-hours per week, pretty much evenly spread across the 3 categories. And we want to reduce that by a factor of 10 to 300.

Even if you avoid public transport (which has other negative implications for the next major disaster of climate change heading our way) you don't get anywhere near. Carry on as before and drive to work and you only get from 3,000 to 2,000, nowhere near the 300 desired.

As far as I can see, the only way to even get close is to not go in to the workplace, which cuts out the commute part as well. And, in addition, cut down the play component and take all the face-covering and social-distancing precautions when you do.

I see no possible scenario in which widespread full-time return to the office can possibly be entertained as being safe.

Even if we use the idea of only some people going to the office 1 day a week, you're still using up a very significant portion of your contact budget.

Of course, there are those who do need to go to a workplace. There are those who do need to commute. That's even more reason why those who can work from home should do so, to give a bigger allowance to those who really need it.

You can, very roughly, estimate your own exposure. For example, I went out to Ely and had a guided walk with a group of a dozen people or so around the town today. Socially-distanced, including the travel and an outdoor lunch, that was something near 50 contact-hours.

Sunday, August 23, 2020

Does Covid-19 matter if people would have died anyway?

One thing that appears commonly in reports of deaths due to coronavirus is that those who died were elderly or had underlying health conditions.

Partially based on this, there seem to be a lot of people making or supporting the argument that Covid-19 doesn't matter because it only kills ill or elderly people, and they would have died anyway.

How true is this?

Not true at all, as it happens.

You can easily see this from the ONS figures of excess deaths. Consider the extreme case, if they had died from Covid-19 1 second earlier than they would otherwise, then the deaths would have been reported as normal and there would have been zero excess deaths.

So, the existence of excess deaths indicates that those who died had their lives cut short. But cut short by how much?

If we take the main peak as being in April, then the fact that we're still seeing a significant excess indicates that most of those who died would still be alive now. So, before Covid-19 came along they clearly had those months at least to look forward to.

The term is displaced mortality. Basically, if people die at one point in time, then their death won't happen at a later time. Because everyone dies eventually, all the deaths in the April peak will result in a reduction in the numbers of deaths at the point when they would have died normally. So that peak will translate into a trough at a later date.

Given that we had roughly 60,000 deaths in the UK, and assuming 50 weeks a year to keep the numbers simple, then if the average remaining life expectancy of those who died was 1 year, then we would now be seeing a reduction in the current death rate of about 1,200 a week.

We're not seeing a trough anywhere near that size. If the average remaining life expectancy of those who died was 10 years, then we would now be seeing a reduction in the current death rate of about 120 a week. That would be plausible, given the current numbers.

About the lowest average remaining life expectancy consistent with the current data is something like 4 years - which would lead to a drop in the current death rate of 300 deaths per week. We're not seeing that, but it's something you could fit into the uncertainties.

In conclusion, those who died as a result of Covid-19 weren't at death's door, they would have had years of life to look forward to.

Sunday, July 05, 2020

Early employment

I think I had a paper round in my early teens, but that was only a few weeks. They changed the scheme almost every day, and then decided to get rid of the paper boys and girls entirely.

My first proper job was 5 weeks in the summer of 1980. The company was called William Watts, a small engineering firm selling machine tools. At the time they imported machine tools from East Germany - while not quite as good quality, they were massively cheaper than the competition.

(They went out of business, but I found Millbrook Machine Tools who appear to be the follow on company.)

My job was to be general assistant to the showroom manager. Cleaning, tidying, whatever came along. In my first couple of weeks I - essentially unasked - went through their entire stock of leaflets and brochures, tossed the rubbish, sorted and organised it. I think this was the first time they had employed anyone for the summer holidays, so they were probably expecting some idle yob. I ran out of work in the showroom very quickly. They then set me on tidying up the finance store cupboard, which they had just thrown all the old paperwork in for years and now needed to move everything because that room needed to be used for offices. A couple of days later it was in its new home, neatly sorted by date too, which astonished them.

The union rep complained to management that I was showing everyone else up. Of course, the thing was that they had (without thinking about it) given me tasks for which my ordered and methodical mind was perfectly suited. But there was never any problem - I got on really well with all the staff, and the union rep even made sure I got the holiday allowance I was entitled too. For the remainder of the time I was the extra help in the spares and repair office, covering for the regular people who were on holiday. The thing about the East German machine tools was that getting spares was a nightmare, so we held a stock of what we could get and manufactured anything else ourselves. And the stuff kept breaking down, so we had a stream of calls for replacement parts, so it was just a case of finding the right thing in the warehouse, and packing it up to be sent out.

My next summer job, along with a few classmates from school, was with a small company called Midlands Educational Technology. (They were a branch of TecQuipment.) The company made demonstration engineering models - some of them very simple (I helped make a batch of carburetors mounted on a baseboard), and some very upmarket like the cutaway cars you might have seen in showrooms. Another thing they did was to take engines out of scrapped cars (I think it was mostly Ford Escorts), strip them down and clean them, and then assemble them to be sent out to technical colleges where students would repeatedly strip them down and put them together for practice. This was pretty hands on, and a lot of fun.

There was a bit of bother with an industrial dispute. The union here were a bit more militant, and called a strike one day. Of course, the small group of students couldn't go out on strike, as we weren't members of the union and would have been fired on the spot. There was one poor chap who had forgotten to join the union, so he sat with us as we just twiddled our thumbs and drank sweet tea while the union and management had a pointless argument.

Because TecQuipment were an educational company, some bright spark came up with the idea that they could get us students to test out some new electronics kits they were thinking of becoming a reseller for. This was really cool, instead of a breadboard you simply slotted clear plastic cubes into the right layout on a grid to get a working circuit. It was quite neat because the plastic cubes had the electrical symbols printed on the top so you ended up with something that looked like a proper circuit diagram. The instructions were terrible, and half wrong, so I corrected my copy (remember, I'm a physicist). They were sufficiently impressed that they offered me a proper job.

I worked out at TecQuipment's head office, in the R&D lab, for my year off between school and university. (Actually, 9 months, as the Oxbridge entrance exams and interviews were in early December.)

If you look at the TecQuipment heritage history, under the 80's it mentions the Queen's Award - I remember going to that ceremony - and expanding exports. Specifically, Mexico. The company had managed to win a huge order to supply educational materials, covering pretty much its entire range, to Mexico. In the small print it had something about the equipment being supplied with adequate documentation. Enter me, just having left school, suddenly responsible for getting all the documentation ready.

Well, it didn't work out like that. In many ways, I was ideal for the task they thought they had, of simply finding and checking the instruction manuals before sending them off to be translated. The problem was that much of the documentation had either never been created at all, was for an old version of the product, or had been lost entirely (in some case we ended up finding prior customers and getting the manuals back off them to get a copy). It wasn't just documentation, of course, in some cases they had managed to sell models they hadn't made for years and had lost the plans for. The whole Mexico project turned out to have been hopelessly underestimated - in the end they had a whole department of engineers and a bank of secretaries typing away.

I was taken off Mexico and put to work on other interesting projects. We had a range of robotics and did some open days touring schools. We had the usual cheesy robots, and I remember there was a programmable speech synthesizer called ChatterSphere that was a big hit.

I also ended up being effectively in charge of the Chemistry products. This was really odd because I'm a physicist and mathematician, and hated chemistry at school. But we didn't have anybody else in the company who understood any of the chemistry products anyway - they were designed by a University Professor - so I was as good as anybody else, and using me avoided having to take a real engineer off the Mexico project. One day we got one of the odd requests that make life interesting - one of our enterprising salesmen had agreed to sell a product that was made by one of our competitors for half the price. Could we make some real quick?

This was a simple corrosion tester. Ultimately, you had some jars of water (potentially with salt or other chemicals in), and you simply dangled samples in the jars to see what happens. Add some means of heat (a portable electrical cooker ring) to vary temperature, some means of varying the oxygen content in the water (we went down the road to a pet shop and got an aerator for a fish tank), a digital scale to measure the change in mass of the samples, some pretty framework, and it was a great success. About the only guide I had was a page ripped out of the opposition's catalogue - we had to make it close enough to make the customer happy, but different enough not to make it too obvious it was a knockoff.

Tuesday, June 30, 2020

Panic buying or inflexible systems?

Early on in the coronavirus pandemic, the shops ran short of supplies.

There was no sanitiser gel to be had for love or money. Of course, there was wall to wall messaging about how important hand washing was, and how you should use sanitiser if you couldn't wash. Shortage of supplies in the shops means that people were paying attention.

Basic food supplies - pasta, flour, and the like - were scarce. Everyone looked at what was likely to happen, decided that the likelihood of needing to feed themselves at home without being allowed out was pretty high, and put an extra item or two in their basket.

I'm not quite sure how much toilet roll people thought they needed, but being stuck at home means you're going to need more.

I think there's fairly widespread understanding that the the term panic buying was completely misleading. This was (and there will always be the odd exception) a simple adjustment to changing circumstances.

Or, rather, a couple of changes.

The first is that being at home more means that you need more of almost everything. More food, more household supplies. Less petrol in the car, at least for most of lockdown.

Of the 100 days or so we've been locked down, we would normally have been on holiday or a trip for something like 7-10 days. And we would probably have gone out to a pub or restaurant for a meal 5-10 times in addition to that. So that's between 10 and 15 days that we wouldn't have been at home - eating or using other materials. (The Cambridge Beer Festival would have added a whole extra week to that, but that's a slightly exceptional event.) Just because of that, our weekly supermarket spend is going to be up 10-15%.

Other people won't necessarily have the same specific changes, but a lot of people eat out, use takeaways, get schools to feed their children one meal a day, or grab food on the go. So the idea that demand on supermarket supplies in general might be up 10-15% seems plausible.

Recently, Tesco have reported about a 10% increase in demand, which aligns with this. Of course, pubs and restaurants are seeing the other side, with a precipitous drop in income. The overall amount of food required doesn't change, it just gets into peoples stomachs via a different supply chain.

And the supermarket business is pretty cutthroat. The supermarkets have spent years optimising their supply chains to stay competitive. None of them have the slack in their systems to cope with a sudden 10% uptick in demand - if they kept that much headroom in normal operation they would get wiped out in short order.

The second change is in when people shop. We always used to shop twice a week. This is good, you get fresher produce and each shopping trip is more manageable. But now, and this seems to be general, we're making fewer - but obviously larger - shops.

The shift from twice a week to once a week means there's going to be an initial surge. That first shop will have half a week's extra stuff in it, and you end up with everyone having half a week's worth of additional supplies. And just the knowledge that you can't (or won't) simply nip in if you run out means that you're obviously going to have to stock up a little earlier. So there's this sudden surge to add 3 or so days worth of food. Once it's stabilised, of course, it goes back to normal.

We haven't gone for online shopping yet, for the main shop anyway. The supermarket is only a few minutes walk away so it's pretty silly for us. What we have used online ordering for is some of the more specialist items that the local supermarket doesn't carry - the luxury of being able to visit multiple stores is one we've avoided for now.

Longer term, I think it's going to continue in the current state for a while. I really can't see a widespread shift back to pre-pandemic behaviour. People will go out, of course - if only because they're a bit stir crazy - but the idea of going out will soon lose its charm. The hospitality sector is probably going to have to reinvent itself entirely.

The changes we've seen didn't result in the overall volume of demand changing, just in where and how it appeared on the demand side. We have the prospect of the ongoing Brexit fiasco disrupting the supply side, stressing the system again.

Sunday, May 31, 2020

On being under lockdown

A while ago I wrote about On working from home.

Of course, the recent COVID-19 crisis has meant that a lot more people are working from home. Although we have to be honest and say that this isn't the normal working from home, it's having to try and work in isolation away from the office because of the pandemic.

Even for those of us used to working from home, this isn't normal.

When I decided to work from home, one of the things I had to consciously think about was how to manage the process. Without the need to leave home and interact with other human beings that comes with working in a shared environment, getting out of the house and going to lots of events was key - museums, talks, meetups, and the odd beer festival. Pretty much all of that has gone out the window.

It's unfortunate timing too. As a general rule things are quiet in the winter months, the weather and lack of light don't help. So I was just looking to come out of mini-hibernation when the pandemic comes calling.

I'm fortunate that the actual work part doesn't change much. The at home has been quite different. Mrs T has also been stuck at home, so I don't get the house to myself during the day. I mean, I like her around, but she has been getting underfoot a lot. (Not to mention the occasional call for IT support.)

Far more so than myself, she's gone online to socialize in a big way. We professionals might turn our noses up at Zoom (and expecially its security) but you have to concede that it's ideal for consumer chat. Even better, and unlike pretty much everything else, it works great on my old retired iPad, which has been heavily used. She's done quizzes, wine tastings, cocktail classes, cookery demonstrations, singalongs, dancing(!), afternoon teas, and just general chat.

Shopping has changed. We're fortunate in that we have a big supermarket just round the corner. Rather than the traditional minor shop twice a week, we've switched to a major shop every 8-10 days. Slightly oddly, as there's more in each shop, we now walk there and back (Mrs T does the shop, I walk over later to help carry it). The cars are basically gathering dust.

Where we are on the outskirts of Cambridge is fairly quiet anyway, but is now even quieter. The buses look empty, the roads are quiet. We go out for walks for a bit of fresh air and don't have to worry about keeping clear of crowds of people. (I'm a bit limited in this, hay fever discourages me from going outside too much.)

The Cambridge Beer Festival was cancelled. That's another major social event gone. Not to mention the volunteering time (minor for me, rather major for Mrs T). And the beer, and the food - especially the cheese! The festival organized a number of online events through the week, and we got in a good stock of cheese (I can strongly recommend Shepherds Purse, especially if you're a fan of blue cheese), found some good beers (or cider) online, and raised a glass at home.

Looking to the future, it's going to be a long time before anything approaching normality returns. There are always going to be those who just can't be bothered with the restrictions put in place, but I'm likely to be a hermit for a while yet.