Neo-Vikings have been plotting the non-viking world's downfall for quite some time. To this end they have designed a super virus, Tryggvason, and are trying to pick between three three countries, the US, Germany, and England. They want to weigh the impact of the virus before they pick a target.

The question becomes: What's the fewest people (as a percent of the population) can the Neo-Vikings expect to die from this virus in the short term to force the country into the levels of economic collapse associated with the American Dust Bowl/Great Depression?

This question concerns the selected country's market, and not the global market.

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    $\begingroup$ I think it depends on how well targeted your virus can be. If it only wipes out the extreme cases in the spectra of age and wealth, (children and the elderly for age) and (welfare-recipients and the leisurely rich for wealth), it could take out a large percentage of the populous without affecting the economy at all. On the other hand, if it targeted working age, working class people, a much smaller percentage of casualties would do a much higher amount of economic harm. $\endgroup$ Aug 4 '16 at 21:50
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    $\begingroup$ I think you would need virus with very low or no causality and very high infection/illness rate, if you want collapse the economy your goal is that they self-cannibalize, huge unrest causing theft, raids, protests, dip in investment, currency crashes, trades are halted/broken. Economy depends more on having hope than number of people in the system. $\endgroup$
    – Chinu
    Aug 9 '16 at 4:47
  • $\begingroup$ look at population density as well as Markets to see the effectiveness of the virus... the UK only has a sixth of the population of the US but that is crammed into the size of a single state, with an eighth of them in one city $\endgroup$
    – Chris J
    Aug 10 '16 at 7:57
  • $\begingroup$ Nex can you define a target and its general info/stats? The answer kinda depends on who you are attacking. An agrarian society would be more impacted than a highly industrialized society and I am not sure what you are looking for. $\endgroup$
    – James
    Aug 10 '16 at 15:12
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    $\begingroup$ It would also help to understand what end-state you are looking for. Sure the great depression was a bad time, but to say that made the US a conquerable country is not accurate. $\endgroup$
    – James
    Aug 10 '16 at 15:14

This is a very difficult question to answer, since some of the effect will depend on the social institutions and cohesion of the society being attacked. Generally, the more cohesive a society is. the more resilient it will be as well. Great Britain survived the Blitz, NAZI Germany actually increased industrial production despite "round the clock" 1000 bomber raids in 1944 and even Imperial Japan was considered to be a tough nut to crack after massive and virtually unopposed firebombings in 1944/45 (Operation OLYMPIC, the proposed invasion of the Japanese Home Islands, was built around an assumption of 250,000 allied casualties, to give you an idea).

Even greater catastrophes have changed societies in subtle and unexpected ways. The Black Death is considered to have killed something like 1/3 of the population of Europe, yet European societies did not collapse. The severe labour shortages caused by the massive casualties did cause Feudalism to collapse, as serfs simply could not be kept on the land when there was far more remunerative work.

If the invaders simply want to launch their invasion during the times of peak disruption, then once fatalities rise beyond 5% of the overall population you will probably find your window. Emergency services and health care will be overwhelmed, the industrial economy will be reeling due to absenteeism, and there will be a significant outflow of people from cities trying to escape the plague. Society hasn't collapsed at that point, put it isn't functioning at peak efficiency either. Military units are generally considered to become combat ineffective at about the 10% casualty mark (they will still stand in place and fight, but generally won't advance) and after they reach 25% casualties they will generally be broken and routed, although against a biological menace this figures may not be accurate.

I suspect that the amount of economic collapse is not going to be quantifiable in the short term, since there is no accurate way to predict which industries will be affected or by how much.

  • $\begingroup$ These are very interesting statistics you're providing, though I'm very curious, could you give your source about the % of population needed to make the economy turn at peak efficency or an army to be broken and routed please ? Thanks. $\endgroup$
    – Kaël
    Aug 5 '16 at 9:35
  • $\begingroup$ The 5% figure is from emergency management. In the courses I took it was apparent that services could be overwhelmed when 5-10% of the population was suddenly involved. Complimentary evidence is from looking at nations with national call ups for the military like Israel; the economy is severely disrupted when the fighting age population is called to war. $\endgroup$
    – Thucydides
    Aug 6 '16 at 2:03
  • $\begingroup$ Military casualty figures are historical "rules of thumb" since the subject is not fully investigated, but SLA Marshall's "Men Against Fire" suggests that an ordinary WWII unit only has @ 10-15% of the men actually engaging the enemy with weapons, and put to 15% in an elite unit like the Airborne, so it doesn't take a lot to tear the heart out of a unit. $\endgroup$
    – Thucydides
    Aug 6 '16 at 2:04

Ignoring the initial healthcare needs as those have already been covered.

You're introducing a virus to the system. A virus is most likely to kill or harm the vulnerable, the already sick, the elderly, and the very young.

Why do I emphasise this? because these are not productive people, they are the people already dependent on society. By killing off all these people you're increasing the economic output of the average person. You're freeing up long term resources from hospitals and care homes. You're streamlining the economy, reducing the load from the cost of pensions, benefits etc.

In short, by using a virus in this way, you're likely to strengthen rather than weaken the economy.

Looking at the ONS stats and assuming that you're going to kill off the unproductive, unhealthy, and elderly first. Population is around 65million, working population around 30million. You might have to kill off 50% of the population before you start to effectively weaken the productive capability of the country.

Until that point, all you're doing is freeing up labour from tasks related to supporting society's dependents. You're also freeing up funds from paying for their needs, their benefits and pensions, and their healthcare.

The rates of consumption are another matter, Keynes says we're driven by consumption not production capability and as such the idle 50% are pure consumers. They drive the economy by their needs, without them, who is consuming what the producers generate? On this model the economy starts to fail rapidly in proportion to how many of these consumers are removed from the system.

This however is only a local consideration, much of what is being produced is being consumed overseas not locally. The knock on effect of stripping a large percentage of consumers out of the system can only be measured on a global scale. They are consuming products from across the world, the effect would be a drop in the trade deficit and a lot of complex calculations relating to the values of currencies.

We haven't yet managed to put a big dent in a single economy but we might have triggered a global recession. We're back to having to kill off the producers, the toughest and the healthiest and the last to die of a viral outbreak. At the upper end, you could be looking at killing off well over 50% of the population.


There's actually a way out of this problem. There's a range of viruses that kill as much by immune overreaction as by the effect of the virus itself. Spanish Flu being a key example of this. Not just because of how many it killed, but because of who it killed.

An unusual feature of this pandemic was that it mostly killed young adults. In 1918–1919, 99% of pandemic influenza deaths in the US occurred in people under 65, and nearly half in young adults 20 to 40 years old. In 1920 the mortality rate among people under 65 had decreased six-fold to half the mortality rate of people over 65, but still 92% of deaths occurred in people under 65.

A virus like this could rapidly cripple the economy, but you're unlikely to be able to contain it enough to protect your own people.

  • $\begingroup$ Yeah, that's huge factor. Really going to depend on how the virus is designed--but all diseases I know of tend to take down those not in the workforce FIRST. I forgot completely about the impact of pensions! That's actually going to further strengthen the economy. $\endgroup$ Aug 10 '16 at 15:21
  • $\begingroup$ @ErinThursby pensions and long term healthcare. Care of the elderly is a massive part of the budget and time use in the NHS. $\endgroup$
    – Separatrix
    Aug 10 '16 at 15:33

Don't Look at The Great Depression as your model, look at instances of hyper-inflation, because that would be the actual effect of this circumstance.

The dustbowl/Great Depression is not analogous in this case, because a lot of that was caused by weather, as well as economic factors. It is quite difficult to tell what will happen because it's hard to predict.

But we can look at what happened as a result of the Black Death in Europe, which took about 1/3 of the population (or more in some places, up to 60%-100%). Weirdly, the Black Death was the cause of upward social mobility for peasants. Because of the labor shortage, human labor was more valued:

Before the plague, the large population kept wages from rising. Most peasants did not consider leaving their villages to find work somewhere else. After the plague, workers asked for higher wages and better working conditions. Many lords agreed to these demands, and those who didn’t soon found that other lords would. Lords began to realize they had less control over workers and began to change what they produced. Many workers were needed to grow and harvest grain, so some lords began to raise sheep instead. Raising sheep required fewer workers and there were more customers for the meat and for woolen clothing. As their incomes rose, people were able to buy more vegetables, fruits, and clothing. Production of these goods increased. Peasants eventually became free to move away from estates owned by lords; some were even able to buy their own land. Ref

So the effect might actually surprise you, and be the opposite of what's intended. Less people means that there are more resources for the ones who are left and it means that the employers who are left are more willing to pay more. For the economy to actually break down completely, (which would be far past the Great Depression) you might have to take things to zombie apocalypse levels, so that there's no one left to run anything, and the streets are filled with dead bodies.

The rising wages will eventually cause hyper-inflation. This is the opposite of what happened during the Depression, when unemployment was high. But this can sink an economy as well. Be cautious, because before it sinks, it's actually going to strengthen.

So, you're going to have to take a look at what high inflation markets do instead of (as with the Depression) what ultra-low inflation markets do. Something like Greece in 1944 or Germany in 1923 or a host of other examples. Things got bad in these places (prices doubling every few days, people stockpiling goods rather than money) but the Great Depression, which dragged on for 10 years, was not as damaging as these events. And governments today have a slightly better understanding of inflation.

I believe that your virus can cause chaos and devastate the population, even drive prices up, however, even during the Great Depression, we still functioned as an economy. Not well, but--we did.

You are looking for an exact number, but that's really, really going to depend on the specifics of the economy in your world/those countries. Factors to consider:

  • unemployment numbers as they stand before the virus. The death percentage will likely have to exceed those.
  • The Age of the People dying. Exceed the unemployment numbers with deaths from virus, and it's going to have to be more than by a percentage point or two. The very young and the very old die in disproportionate numbers, and they aren't in the workforce, therefore they won't actually impact the economy in the same way. You have to match or exceed the unemployment rate with the percentage of deaths of people IN the workforce. As Separatrix says in hir answer, not having to pay pensions will actually be good for the overall economy and governance.

  • Individuals. There are people who are lynchpins, who can save and understand economies. If those people are the first to die, it will help speed them on their way.

  • Time. How much time are you looking to have pass? This is a big, big deal when asking the question. Because temporary circumstances are different for an economy than things that go on for a year or three, or keep returning. This has an impact. You are going to have answer what you want on time goals, for this sort of breakdown.

Sorry that I am not giving you an exact percentage, but, there are many factors to consider and things you should be looking at before getting to that number. I hope I have answered the question insofar as what models you should be looking at and what questions you should be answering in order to arrive at a conclusion. I do believe that your numbers are going to have to be larger than you would expect in order to cause a collapse of this nature and that these deaths will actually improve the economy if the number is too low.


I'm going to base my answer on unemployment and hospitals.

The Great Depression resulted in an unemployment rate of 20-25% in the USA, Germany, and Great Britain. Nearly 1/4 of the people normally employed were removed from the labor force.

So that would be an upper bound of the number required, ~25%, remove that many people and you will have a definite reduction in labor force. Resulting in a depression similar in scope to the Great Depression.{1}

Now death from a virus is going to have many add on effects, that are going to be hard to quantify. Things like fear and self imposed isolation would negatively effect the economy most. When people stop going to work, because the virus is running unchecked in the streets, your economy has effectively ceased to function entirely.

A major contributor to fear and panic would be the availability of medical treatment (even if ineffective). Depending on the length of incubation and treatment timelines {2} your hospitals and medical facilities will likely rapidly be overloaded. An interesting number I found for a study of this is a World Bank analysis of hospital beds per population.


Numbers of hospital beds per 1,000 people as of 2011

  • USA - 2.9 (0.3%)
  • Germany - 8.2 (0.8%)
  • GB - 2.9 (0.3%)

All of these numbers are mostly trending downwards over the last half century.

In a major pandemic these medical services would likely be expanded, but given a 1% rate of infection requiring hospitalization (fatal symptoms) this would completely overcrowd existing medical capabilities, shutting down treatment and setting up a panic. So I'm going to peg the low fatality number likely to shut down a countries economy at 1%

So the number is likely to be somewhere between 1% and 25%

{1} I'm willing to accept that the currently unemployed could take places opened up by deaths and choosing to neglect them as not really significant, if your country has a population with 25% unemployed people to hire, you are likely already in a depression.

{2} I'm assuming people don't just drop dead but get sick and show symptoms and seek medical treatment. This is more likely as a very fast killing disease doesn't spread very well as no carriers are left alive.


I'm not at all sure this is possible, see for example https://eh.net/encyclopedia/the-economic-impact-of-the-black-death/ - less population historically meant more resources/jobs per capita. This might have changed (or if not might change in the future) with the rise of networking (data economy, etc.), and some kind of recession is possible, but as long as it is possible to keep the critical infrastructure going (mostly power, water, fuel and food distribution) I think that a long term per capita economic collapse might not be possible.


As it does not say in your question what the target of the virus is, I am going to say that the virus targets crops (fruit, vegetables and grains etc.) and farm animals, instead of people. This would include spoiling of stored food products that are exposed to the virus too.

In this case, the virus will directly kill 0% of the population in the short term, but will easily cause economic collapse. Obviously it may indirectly cause starvation if the destroyed food is not quickly replaced.

Assuming the virus rapidly attacks and destroys all food production in the target country, but not that of its neighbours, I would list the targets, from most vulnerable to least, thus;

  1. US
  2. UK
  3. Germany

The US would be most vulnerable as I imagine (I have only found US food import numbers online) it is mostly self-sufficient for food production (having a relatively large amount of farm land) and so would be most affected by having to suddenly import all food required to feed the larger US population.

The UK is second as it already imports a lot of food (my trips to the supermarket are my experience of this), so making up the difference to importing all food would not be as big an implication as the US, but as the export of food from the UK would be affected too, then it will still probably cause an easy financial collapse.

Germany is still part of the European Union (where as the UK is on it's way out) and so would have a large number of neighbours to import food from, who may import for free, or for deferred payment and so it is least likely to be impacted by collapse of it's food production.

As I mentioned above, the direct fatality rate would be 0% and the level of financial problems experienced depends on the friendliness of the country's neighbours if/when they sell food to the target.


I think to answer your question, you should look at how the virus is spread. Assuming it is communicable, does it have to be ingested, breathed, or just touched to infect? Airborne and contact viruses would be the most effective, so assuming this to be the case, the most effective method of distribution would be mass transit stations. To get the most distribution you would want a distribution hub that affects the widest geographic location possible - airports. International flights would be ideal, so you are looking at only a few in each country.

Great Britain would be the best target in this regard. While it is the smallest in population - only 65 million - London Heathrow airport serviced more than 75 million passengers in 2015, with 69 million of those being international. Among the top 5 most popular destinations are New York, US - 324 million - and Hong Kong, China - 1.1 billion.

Assuming this is a super virus, you would want it to to be fatal, but not quick - it needs to lay low and infect as many people as possible before killing its host. Let's assume an incubation period of 48 hours, a prodromal stage of 24 hours, an illness stage of 3 days and fatality within 24 hours after that. That gives you 7 days, give or take, before the first passengers die from infection.

London Heathrow services more than 250k passengers/day, with most of these being international. If Tryggvason has an incubation period of 48 hours, that's more than 500K passengers being infected in 2 days before symptoms even start. Those 500K passengers will have interacted with cabbies, family, coworkers, friends in that time, easily doubling or trippling the infection rate in the first 48 hours.

By the end of the first week, when the first infected start to die, more than 1.7 million people will have been infected just at the London Heathrow airport. Forget about local markets - New York's JFK services a similar number of passengers with half of them being international. Hong Kong International is not nearly as busy, but the population around the airport is huge.

In the first 2 days of the virus being released, your looking at 3 -5 million infections, easily. By the end of the first week, before the first death occurs, you are looking at 10's of millions infected across the globe.

Local markets will be the least of your concerns. Just make sure all the vikings are immunized before releasing, because this thing will go pandemic in a heartbeat.

  • $\begingroup$ Hong Kong is an interesting case. The surrounding population is 7 million. HK is a Special Adminstrative Region of China. Access to China is reasonable, but not entirely automatic. 100% of its air traffic is international though. This makes the spread of the epidemic more assured. HK International is not to be sniffed at. $\endgroup$
    – a4android
    Aug 11 '16 at 13:06

(Really a comment but it won't fit) There's a factor that's not addressed in your question: Timeframe.

The faster the virus works the more damaging it will be. Lets take the snail virus: It kills .1% of the population every year. In a millenium it will have killed a total of the world's population but with basically zero economic consequences.

Compare that to the hare virus, equally lethal but it kills .1% of the population per hour. There won't be an economy left to be talking about.

Obviously these are unreasonable extremes but they serve to show that the same kill count can vary between no meaningful effect to utter catastrophe.

Beyond that, the faster it kills the more economic disruption there will be from people trying to avoid the virus. When the news reports start talking about the hare virus you'll have a lot of people hunkering down or getting away from population centers. This will cause a lot of absenteeism and disruption of the logistics of life. (If you know there's a virus about that has a 1% chance of killing you how many would go out their front door for anything less than a life-or-death threat? And how many more would go out but then not re-enter until things were safe again, simply leaving supplies and then backing away.)

On the other hand, the same total death toll spread over years would have little absenteeism because it's simply not viable to live like that for an extended period.


Here is a number: When about 50% of the people usually working at a critical part of the infrastructure are not able to work, severe outages are to be expected. This happened in August 2013 at the Mainz railway control centre (in German) where 7 out of 15 traffic controllers were absent (due to vacations or illness) and the Mainz main train station was taken off the railway net for some time.

The trend towards "just in time" production and "lean mangement" may make infrastructures more vulnerable in future.


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