Wizarding Population

[Robert Shaw]

No: HPFGUIDX 83136

Mikael Raaterova wrote:
> Robert Shaw wrote, in reply to me
>
>
>> The muggle population structure is still showing the effects of
>> WWII, fifty years later.
>>
>> Given their longer lifespans, the wizarding population will
>> be directly affected by events as far back as 1875-1900.
>

Mikael:
> While the population *structure* and age distribution still shows the
> effects of the cohort-affecting events of WWII, AFAIK the deaths of
> WWII and post-war baby-boom didn't affect the population trend, e.g.
> aggregate growth, in any significant way


True, but to extrapolate the wizarding population from Hogwarts
without assuming (in the absence of good evidence) that structure to
be invariant, you do need to known what the population structure is.

> (I'll admit I'm a bit hazy
> on WWII's population effects in the British isles, so I'm prepared to
> be proven wrong; data from 1950 onwards shows only steady increase
> though).

As an aside, much of that increase is actually due to immigration.
How do wizards deal with that?

The Hogwarts' quill records the names of wizards born within range,
but Indian muggle-borns whose parents have just immigrated will not
be listed.

English muggle-borns whose families emigrate to the US when they're
five will cause similar problems

Does the Ministry hunt down immigrant muggle-borns, and notify
other countries of emigrants, or do the muggle-borns in such families
slip through the cracks?

If the ministry lost track of many muggle borns during the
mass muggle migrations of the last centuries this could have
a significant impact on wizarding demographics.

[Muggle migration also mean that even if Catlady's theory
were true, UK wizarding numbers would still change, unless
the deep magic in her theory can predict where the muggle-borns
will be living when they're eleven]


>
>> Furthermore, since a significant proportion (currently about
>> 25%) of wizards are muggle born, any change in muggle
>> demographics will have a knock-on effect on wizard
>> demographics.
>
> Changes in muggle numbers have to be *huge* to affect the number of
> muggle-born wizards.

The change may be huge, but since the muggle population is also
huge this cancels out.

A 5% change in muggle numbers will produce a 5% change in
muggle-born numbers, to a first approximation.

>If we ignore post-OWL dropouts, then 36
> muggle-borns enter Hogwarts per year (in present years), if 25 % of
> students are muggle-borns.

So, e.g, a 5% increase in the muggle population means 2 extra
muggle borns, and the percentage increases to 26%. A 15%
increase would push the percentage to 28% and so on
(though its not actually proportional)

Conversely, if the muggle birth-rate halves one year, as during
the world wars, then only 18 of the 126 students for that year
will be muggle-born (14.2%). If we based our estimates
of wizarding population on Hogwarts today, we'd overestimate
the number of wizards in their sixties by over 10%


>Granted, the muggle population
> has grown a bit over a hundred years, so the generational proportions
> of muggle-borns should be lower in the older generations and higher
> in the younger generations. Even so, if 75 % of present Hogwarts
> students are muggle-borns, it only amounts to about 100 magical
> births to muggle parents per year. Anyway, it's reasonable that the
> vast majority of muggle-born wizards are still relatively young, and
> that muggle-borns will outnumber wizard-borns in the foreseeable
> future.
>

Quite possibly, for a century or so. Poplations projections beyond
that point are iffy, but the muggle born population seems to be static
now.

> Also, I see no reason at all to speculate about changes in the rate of
> births of wizards-to-be in the muggle population since there's
> absolutely no hint of it in canon. Having them be a constant fraction
> of muggle births seems instead a reasonable assumption.
>

I agree. There are factors that could change this percentage, but only
slowly. They can be safely neglected as long as we're not trying to
estimate the wizarding population in 745AD
>

>> The muggle birth rate fall certainly is, which has consequences.

>
> If you don't accept a fairly stable wizarding population, you'll have
> to posit that they have had periods of low mortality and high
> fertility followed either by cataclysmic extermination events or
> equal periods of population decline. I think you'll have trouble
> finding causes for such changes.

The problem is that we know the muggle population has had
major fluctations, which must have some impact on the
wizarding population.

I'll accept fairly stable, but not static, and you need static
to extrapolate from Hogwarts.


> As a conclusion and summary to my points above, it's reasonable to
> assume a) that the wizard-born wizarding population have been stable
> for ages, and b) that the proportion of muggle-born has been
> increasing steadily as a function of the muggle population growth
> Thus we should be quite able to deduce quite a lot from the number
> of students at Hogwarts.

True, within limits.

Going by the student population of Hogwarts alone, we can deduce
the wizarding population with an error of perhaps plus or minus 50%
(not good enough to base any conclusions on)

Take account of shifts in muggle demographics and we can reduce that
error to perhaps 10%, at the cost of complexity.


>  I definitely agree that the muggle
> population explosion *is* a huge change, but it's effects haven't
> reached full strength yet, since muggle-borns are as of yet only 25 %
> percent of the total wizarding population. I don't have UK cohort
> data with which to calculate the likely age structure of muggle-borns

It's all available on the UK census web site.

The more intelligent wizards can probably see the effects of this change
coming, which will be worrying the pure-bloods, with the consequences
we've seen.

--
Robert