[HPforGrownups] Re: Wizarding numbers: 24 000

[Robert Shaw]

No: HPFGUIDX 83348

Mikael Raaterova wrote:
> Robert Shaw, replying to me;
>
>> I'm a mathematician, not a sociologist, but your reasoning looks
>> sound, given your assumptions.
>
> Well, that's a relief. Of course, my assumptions may still be
> invalid, but that remains to be discussed...
>
>
>
>> As an aside, much of that increase is actually due to immigration.
>> How do wizards deal with that?

[Snipped analysis shows immigration makes no noticeable difference
to the numbers, though it could create interesting situations for
the rare people involved].

>
>  Migration don't affect the wizard population in any
> dramatic way,
>
> Sorry, i meant to say *wizard* population.
>
[Snipped analysis confirms given assumptions reasonable for
for the UK]

Lets think about the Colonial US.
Assume, reasonably enough, that no purebloods emigrated.
A few may have done, but they weren't subject to the
same pressures as muggles.

Assume also that native american wizards didn't interact
much with the colonials.

This means that for the first few generations after Jamestown,
most colonial wizards will have been muggle-born, or the
children of mixed marriages. Arrangements may have been
made to get them to Hogwarts, or they may have had only
minimal magical education.

Eventually new pureblood families would have been formed,
and new schools of magic founded, but continuity of tradition
would have been lost.

Migration only makes a major difference to the wizarding population
if it changes the muggle population by an order of magnitude,
because of various damping effects. No such migration has happened
in the UK since at least Viking times, but it has happened in some
of the ex-colonies.


Mikael also said, in reply to me:
>
> The weakest point in the analysis is the die-off function. The
> inflexion point and slopes of the mortality curve is pure guess-work,
> since we have no indication whatsoever of how wizarding age-group
> mortality is differentiated, except that at high ages it has to be
> lower than for Muggles, or the ages of Dumbledore and Marchbanks
> would be impossible.

Looking at causes of death helps refine our guesswork slightly.

The accident and violent death rates spike amongst adolescents,
particularly males. Young wizards are more likely to kill themselves
playing quidditch than driving dangerously, but the effect will be the
same.

Similarly, if some teen wizard finds his girlfriend in bed with his
friend, he's as likely as any muggle to get violent, and rather
more likely to have a deadly weapon close at hand.

(Of course, most adolescents are pretty responsible, but the
overall death rate at that age is low enough that a minority of
hotheads can drive it up significantly.)

I'd therefore guess that the death rate from 15-25 is about the same
for wizards and muggles.

Deaths below fifteenish are pretty rare. Children are disproportionately
unlikely to die in anything except a major disaster. The wizard death
rate will be slightly lowly, but the numbers are so small it won't cause
any significant error to assume that the death rates are the same today.

The difference only shows up once wizards pass 25ish, by when
wizards and muggles have calmed down. A reasonable enough
assumption, partially supported by cross species comparisons,
is that the death rate after 25 can simply be linearly stretched.

I.e, if the wizard life expectancy is 125,  and for muggles 75,
then the death rate for wizards at age n is the same as for a
muggle aged  25+(n-25)*(75-25)/(125-25)=(n+25)/2.

This puts Dumbledore in the wizarding equivalent of
the muggle mid-eighties age bracket, which sounds about
right.

Since there are fewer wizards than muggles, there won't
be the equivalent of the exceedingly rare 120 year old muggles.
I'd put the maximum wizard life span at 100 equivalent,
which is 175.


Mikael then said, again in reply to me:
>
>> Despite the unsoundness of some of your assumptions, I think at
>> least half your conclusions are at least half right. You can assume I
>> mostly agree with everything I cut.
>
> Wouldn't that make my analysis 75% wrong?

Or 100% right, or anywhere in between.
I'm sure some of my conclusions are partly wrong too.

>Quip aside, which of my
> assumptions do you find unsound?
>
Principally, the assumptions about death rates, together
the other unspoken assumptions needed to come to any conclusion.

I know they're necessary, but they still feel questionable.

--
Robert