If 5 million people disappeared at the same time globally, assuming an even spread of random disappearances (not focused in any one location) how long would it be before people noticed there had been a mass disappearance if ever?
Assume the person disappeared with the clothes on their back and whatever they had at the time from wherever they were.
Almost instantly.
While many people in the world live under the poverty line, with little technological ways of letting the world know what happened, 36% of the world population lives in India and China, and on average 1,800,000 of those disappearances will happen there. The density of the population and relative closeness to emergency organizations means that disappearances will quickly be notified to police and hospitals, which will quickly acquire news attention. Since people have disappeared globally, the news from any country will be combined with the news from other countries, and thus spread the word quite quickly.
You are talking almost 1 person in 1500 (there are 7.5*-ish* billion people on this planet, depending on who you ask; but that doesn't really change my point). Noting that you are saying "even spread", that means
There are a LOT of all those things. Which means this will create a LOT of "X-Files". One, might be reported in news of the weird. But when Fulton County, Georgia has 60 of them in the same hour... Different deal. When CNN has 3 people in the building just disappear, yeah, the moment they hear an external report that corroborates their own experience, it's on the air.
-* In the USA alone, figure between 0 and 15 GA aircraft depending on time of day, season and weekend. Most 0-soul crashes will play out like hypoxia accidents; they are trimmed for cruise, and crash [land] when they run out of fuel.
It depends if it's random or selected.
5 million people selected could go missing and nobody really notice but random would lead to questions especially if they were near a camera at the time or driving a vehicle or with other people.
Almost instantly, if those 5 million are randomly distributed.
Many missing persons result in missing persons reports. People compile statistics on those, and they compare those statistics between cities, between states, and between nations.
Someone would say "wow, yesterday we had more than twice the usual number of missing person reports." And someone else would say "strange, same over here." Probably before the amateurs on the internet notice the same pattern.
As soon as its filmed and put on social media. Chances are pretty good that some of these people are going to be on film disappearing. People might think the videos are fake, but they will still be newsworthy if a bunch happen at once and that's going to lead to more investigation(even if only to prove its a hoax) which will reveal that something is happening.
I assume in my answer that the disappearance itself happens unobserved. Otherwise your question doesn't make sense. Because if there were millions of witnesses, the disappearance would already have been noticed.
It will depend on who disappears. Children in most Western countries will be reported missing often within a few hours, and if many such reports come in on the same day, that will certainly make the evening news.
But there are many people in the world, whose disappearance will not get reported immediately. For example:
Many people today in Western countries live alone. If my mother disappeard (who is 88 and living on her own), no one in my family would notice for several days or even week. If the person living alone would be working, the co-workers would notice, but they would probably assume the person was sick and had forgotten to call. They might call after a few days, but they would probably not go to the police for a very long time. I wouldn't.
Anyone on holiday will not be missed until they are due home. That could be a month (summer holidays are quite long is some countries).
Hunters and fishermen in non-industrial countries are out hunting and fishing for many days. My Russian step-father is out in the forest for weeks, sometimes. No one would note that he was gone for quite a long time.
There are migrant workers who no one knows where they are. Where I live, many workers are employed illicitly. Their boss will be annoyed that the worker doesn't show up, but he will certainly not call the police. Rather he will assume that the worker has found a better paying job. And his friends and family will expect him to return home in half a year or so.
Everyone who is self-employed will not be missed for a long time. Clients will call and email, but probably not involve the police, and if they do then they won't report a missing person but fraud.
If my older son didn't come home in the evening, I would think that he had stayed with a friend and gone to work from there. I wouldn't worry until the next evening.
And so on. In all, many people are unaccounted for for pretty long stretches of time. So
And
* Note.
8 million children go missing every year. I cannot find numbers for all missing persons, including children and adults, but let's try to estimate.
Close to 700,000 persons go missing each year in the US. That's about 0.2 % of the population. 38,000 persons go missing each year in Australia. That's about 0.15 % of the population. 250,000 persons go missing each year in the UK. That's about 3.5 % of the population.
If we assume that around 0.2 % of the global population go missing each year, that would be 15 million people each year, or a bit over a million each month. That seems to be a good estimate. In Europe and the USA, about 40 % of missing persons are children. 40 % of 15 million are 6 million. So likely the number of missing persons worldwide is a bit higher than 15 million.
5 more million missing spead over a few weeks would certainly create a "bump" in that distribution, but that bump might not be recognized immediately.
Not too much time, pratically as soon as the first families to realize the disappearance of their relatives spread the notice
5 milion people would mean that about one man every 1.400 people would disappear.
Think that you live in a 5.000 people town and 3 people suddenly disappeared. In such a small town (and thanks to social networks), as soon as their families would note their absence, everybody else would know this and start to wonder why 3 unrelated people had gone missing at the same time.
Moreover, since the first thing to do in these cases would be to notify the police, even a small police department would receive at least half dozen missing reports in a few hours and realize that there is something wrong and alert the authorities.
And since the same would happen also in the small towns nearby, the word would spread really fast... I think that in no more than 1-2 days the disappearance would be of common knowledge.
Most people seem to think it would be very rapid, and cite examples -- people caught on camera, operators of vehicles.
I'm not so sure:
People who are talking to each other on the phone would go, "that's odd" but I think would shrug it off as "boss came around" or "doorbell rang." Most wouldn't realize that something had happened until they failed to reconnect. But it would be odd, most quick disconnects are accompanied with a "Gotta go"
People on facetime/skype would be confused: The view suddenly shifts and the device is dropped. I think many of them would just think "Butterfingers..." but when the camera showed only ceiling, no noise, they would be aware that something happened. I think most people would make a semi-rational scenario for at least a few hours.
People who were physically present in the same room -- meeting, classroom, etc, where you know a lot of the others would notice right away. But picture the conversation when you call building security and say that someone evaporated giving a power point presentation. Strange looks. Water tests for mind altering substances. Lots of statement taking. And who does security report to? I think that each level it goes up the chain will require several hours of "Yeah right" "You don't say"
It won't get real consideration until one person gets reports from several places. Up to that point it's a "Mary Celeste" story. Odd. Unexplained. But unless you are family it's going to be a 15 minute sensation.
Some alterations of your scenario could keep it quiet for longer:
The clump vanishing means that the entire dev team meeting for a code walk through is gone, the entire congregation of the West Horsebiscuit Dutch Reformed Church is gone -- or at least everyone in church that day; Mrs Smith's Grade 12 lit class; Parents vanish in pairs unless sleeping in separate rooms. Bus loads of people, but only when the bus is at a stop or light in a fairly deserted area. Restaurant full of people one instant, gone the next. Waiters in the kitchen left, ones in the dining room gone. Whole families and groups except for the ones in the washroom.
This makes for a bunch of odd events.
The dev team isn't noticed until someone later is missed at another meeting. Bunch of living partners will probably wait a day, "He went out for beer with the boys" but not get really concerned until the next morning.
A missing church congregation is really unlikely to be noticed. Usually whole families will be gone. There will be a bunch of kids marked absent, a bunch of adults who aren't at work. Probably a few people who weren't in church, who complain about people that didn't come home.
Kids who wake up to find their parents gone will range in reaction. Some teens will think, "Great, the house is mine, at least until they come home" Some kids will get themselves off to school. Young kids won't know how to report missing people. Parents who wake up to find "the twins" gone, but Susan still in the house will have reactions depending on the age of the twins ranging from, "What are those two up to now?" to "Sneaking off to their trapline again..."
Class in school will be noticed the next period, at class change, but the next class in that room won't report it; however the noise will likely get someone from administration in, who finds no Mrs. Smith. It will take a while to realize that Mrs. Smith isn't on the school grounds any more. A raft of absent slips over the next few classes will convince the admin that something is wrong. But if it was the last class of the day, it will be supper time before parents start contacting the police, "Mike didn't come home after debate practice last night"
In this sort of scenario I think it would take several days to connect the dots at a town level, and a week or more at the national level. A town of 10,000 will have about 7 missing people. Which may mean some towns are missing a classroom, other towns are business as usual. A city of 100,000 loses 70 people. A bus found empty at a bus stop in suburbia, a missing group from a meeting, an empty MacDonalds.
You're the watch officer for Precinct 6 in East Horsebiscuit. You've gotten an odd call about a disappearance. Dispatch sends an officer to check. It's only as reports trickle up through the system that you realize something is really wonky. A precinct in NYC typically has 100-130 thousand people (77 precincts, 10 million people) So they are missing 70 to 100 people, but many of these will trickle in. By the end of the shift something is clearly going on, but it will take another day to realize there is a real problem, then another two days to get a good handle on the scope of the problem. I bet, however that each city will think that it's a local problem.
In the US there are more than 2 million prisoners. using the 1 person in 1500, rate per the answer by Harper that means that more than 1,300 prisoners are going to disappear at the same time.
There no way for this to go unnoticed.
Less than 10 seconds. As soon as it happens, anybody who has a twitter account, who is talking to somebody while they go missing, will report it.
