How to extropolate a statistic realistically.

[Phyrebrat]

Sorry for flooding the board with questions lately; you shouldn't be so good at answering them

That being said, I have another, and suffering from dyscalculia I need to check in before I commit to this (altho' I got a C in maths, it was a struggle for me - I actually have an arrangement with my sis and father to check my challenge entry word counts each month as 'seeing' numbers is hellacious).

So: If I take the amount of missing people reported in the UK, can I extrapolate for a global figure by multiplying it by the amount of countries in the world? It's going to be wrong if I do that each country has different population densities and I'm not sure what formula I should use. It doesn't have to be exact, I just need a ballpark.

It's not a case of simply looking it up online because I need the character in my wip to work it out on paper, so to speak. It's just a small thing, but I want to include it.

Thanks for any info.

pH

 

[HareBrain]

Amount of missing people in UK divided by UK population then multiplied by world population will give you as close as you're going to get (without taking into account the factors of why people go missing).

So if there are 10,000 missing in the UK (no idea) you'd have 10,000 over 60 million, which equals 0.000167, times 6 billion (or whatever it is these days) = 1 million.

(If your character knows that the UK has roughly 1% of the world's population, he can just multiply the figure by 100).

 

[Phyrebrat]

amount of missing people in UK divided by UK population then multiplied by world population will give you as close as you're going to get (without taking into account the factors of why people go missing).

Thanks Harebrain, that's exactly the kind of formula I was after. I'll try it now.

pH

 

[Ursa major]

Don't forget that if it's your character, rather than you, who's doing the calculation, some leeway is allowed (unless your character is meant to be hot on maths, statistics and geography). So if he or she thinks that there are 6 billion people in the world, or the UK's population is 60 million that's fine**. (You also have to take account of when your story is set, as this will affect the figures, in particular how much of the world's population is made up of those living in the UK.)



** - As of March 26, 2014, the world population was estimated to number 7.161 billion by the United States Census Bureau. The 2011 census gives the UK's population as 63.182 million. It'll be about 64 million by now.

 

[Mirannan]

The hidden assumption is that roughly the same proportion of people go missing in the UK as is the average for the rest of the world. Which may or not be correct, of course.

 

[Phyrebrat]

Don't forget that if it's your character, rather than you, who's doing the calculation, some leeway is allowed (unless your character is meant to be hot on maths, statistics and geography). So if he or she thinks that there are 6 billion people in the world, or the UK's population is 60 million that's fine**. (You also have to take account of when your story is set, as this will affect the figures, in particular how much of the world's population is made up of those living in the UK.)

** - As of March 26, 2014, the world population was estimated to number 7.161 billion by the United States Census Bureau. The 2011 census gives the UK's population as 63.182 million. It'll be about 64 million by now.

The hidden assumption is that roughly the same proportion of people go missing in the UK as is the average for the rest of the world. Which may or not be correct, of course.

Thanks, Ursa & Mirannan for the figures and the advice; he is très laissez faire and his comment is more about him making a point, so he acknowledges his figures are probably general - and wrong

pH

 

[JonH]

Be careful not to mistake the number of people who go missing with the number of missing people or the number of people reported missing.

People report others missing. In the UK, there are over three hundred thousand reports. But the same person is often reported missing by several other people. So far fewer actual incidents take place. About quarter of a million incidents of people going missing. But the same person can run away more than once in the same year. So the number of people "going missing" is a little fewer than two hundred thousand each year.

And not one of these stats give you any idea of how many missing people there are out there.

In the UK you don't have to wait twenty-four hours before making a report, especially if the missing person is under eighteen, and a hundred thousand of them are. Most of them return within two days.

70% return within 16 hours
19% in 16- 48 hours
2% remain missing for longer than a week

So of the 250,000 people, at any one time there are about 550 people missing who are short term missing people, that is of the 98% who return within a week.

About 5,000 people go missing long term every year. But they don't all mount up forever. About 350 unidentified bodies or parts of bodies are found every year, so they remain as missing on the stats, even though they aren't.

In total about 16,000 people have been missing for over a year. You can assume that at any one time around eighteen to twenty thousand people are missing.

These estimates vary. I've taken a lot of these numbers from the official police reports, and from the missing persons web sites. Unfortunately the most accurate of these figures is the smallest, the 550 short-term value. The long term values are very much guesswork by different agencies.

Fewer than 30% of the reports get put on a central database.

Can you reasonably extrapolate this to other countries. In my opinion not a chance. But if we are so finger in the air guesswork in a major first-world country, who will be able to tell how accurate you are if you do?

There are seven billion people (ish). 65 million in UK. So if eighteen thousand are missing in England, and you just used the same ratio, you'd get about two million people missing around the world as you read this.

 

[Phyrebrat]

Be careful not to mistake the number of people who go missing with the number of missing people or the number of people reported missing.

People report others missing. In the UK, there are over three hundred thousand reports. But the same person is often reported missing by several other people. So far fewer actual incidents take place. About quarter of a million incidents of people going missing. But the same person can run away more than once in the same year. So the number of people "going missing" is a little fewer than two hundred thousand each year.

And not one of these stats give you any idea of how many missing people there are out there.

In the UK you don't have to wait twenty-four hours before making a report, especially if the missing person is under eighteen, and a hundred thousand of them are. Most of them return within two days.

70% return within 16 hours
19% in 16- 48 hours
2% remain missing for longer than a week

So of the 250,000 people, at any one time there are about 550 people missing who are short term missing people, that is of the 98% who return within a week.

About 5,000 people go missing long term every year. But they don't all mount up forever. About 350 unidentified bodies or parts of bodies are found every year, so they remain as missing on the stats, even though they aren't.

In total about 16,000 people have been missing for over a year. You can assume that at any one time around eighteen to twenty thousand people are missing.

These estimates vary. I've taken a lot of these numbers from the official police reports, and from the missing persons web sites. Unfortunately the most accurate of these figures is the smallest, the 550 short-term value. The long term values are very much guesswork by different agencies.

Fewer than 30% of the reports get put on a central database.

Can you reasonably extrapolate this to other countries. In my opinion not a chance. But if we are so finger in the air guesswork in a major first-world country, who will be able to tell how accurate you are if you do?

There are seven billion people (ish). 65 million in UK. So if eighteen thousand are missing in England, and you just used the same ratio, you'd get about two million people missing around the world as you read this.

Hi JonH,

Thanks for such a detailed reply (where were you when I was taking my GCSE maths?? ).

The character doesn't need accuracy, he needs to proselytise about how he would work it out. Whether he gets it right or wrong is immaterial, in fact it's actually better that it will be wrong. Essentially it's the calculation he was after, not the answer; certainly not an empirical one.

Your comment of missing people vs people who go missing is a nice one, though, and I'm going to lengthen his line to include that.

I am grateful for your response.

Ph

 

[JonH]

Hi JonH,
where were you when I was taking my GCSE maths??

I refuse to answer, and want to phone my lawyer.