Web Counters
counterGo to Publications CollectionGo to Graphics CollectionsGo to Commentary CollectionsGo to All Things RelativeConcerning the Potterverse Go to The Potterverse UNhallowed

The Rise of the Mudbloods:

JK Rowling never confirmed my original theory that upon the passing of the International Act of Wizarding Secrecy in 1692 all interaction with Muggles became expressly forbidden; only for that ruling to be modified about a century later to allow for the discreet identification, training and recruitment into the wizarding world of Muggle-born magical children.

I am no longer altogether convinced of it myself. I have come to suspect that the formal Act of Wizarding Secrecy hadn’t all that much to do with the matter.

From canon we know only that the Act of Wizarding Secrecy ended the practice of wizards living openly — as wizards — out among Muggles. We also know that the British wizarding world today aggressively identifies, trains and recruits Muggle-born magical children into the wizarding world as a matter of course. We do not know for a fact that this last has not always been the case; although the statutory restrictions upon magical/Muggle interaction makes this sound slightly unlikely.

If nothing else, the enforced secrecy would introduce a considerable roadblock into the process. How are you expected to convince people to allow you to train their children as wizards, when you are not permitted to tell them that you are one?

But I concede that it is still only my own interpretation which proposes that it was the security risk inherent in the increasing incidents of accidental breakthrough magic generated by Muggle-born magical children in the early factories that convinced the Ministry of Magic that the risk of contacting such children’s families and letting them in on the secret was less dangerous than the risk of leaving matters as they were. Nor can the Hogwarts quill, now in the keeping of the Deputy Headmaster (or Headmistress) have ever been invented for any other purpose than that of identifying those Muggle-born magical children who would otherwise have been in danger of falling through the cracks. Rowling has not confirmed this reading of mine either. Nor will she.

Still, at first, or even second glance, everything we have been shown in canon appears to support this interpretation.

But, it somewhat belatedly occurred to me, that a more recent after-the-fact redefinition of the term “Seclusion” was not absolutely necessary to this interpretation of the history of wizards vis-a-vis Muggles in the Potterverse.

For one thing, it seems obvious that at any time since the Seclusion of wizards was established, any Muggle-born magical child who was identified would have been offered a place at Hogwarts, and a future in the wizarding world. The catch is that; since most wizards no longer lived out among Muggles, or interacted with them any more than could be avoided, once Seclusion had been established, apart from the vicinity of the half-dozen or so semi-wizarding villages in Great Britain, such children had almost no chance of being identified.

Consequently, the real watershed would not have been the date of any hypothetical “relaxation” of the statute, but the date at which the Hogwarts quill went into commission.

And even then the resistance to the sudden inclusion of a large number of Muggle-born wizards into wizarding society may have been far less than the modern isolationist attitudes might suggest. For it is likely that, at the beginning, there may not have been nearly so many Muggle-borns to contend with.

Or it may have looked like simply one large group to be incorporated all at once, and take care of all of the backlog in one fell swoop.

However; over the course of the 18th, 19th, and 20th centuries the rise in the Muggle population of Great Britain would have dictated a corresponding rise in the Muggle-born magical population of those islands as well. To the point that by the end of the 20th century Muggle-born magical births roughly match those of pureblood wizards 1:1. Now, admittedly, with each successive generation the pureblood segment of the total wizarding population probably diminishes slightly, but the pureblood isolationist faction turns out to have ample reason to feel itself under siege.

Particularly if one factors in the possibility that with the burgeoning rise of Muggle population over the last 300 years and the increase of Muggle longevity in the last century, the Muggle population is in danger of crowding the wizards out, and making it ever harder for them to live in any kind of isolation, without detection.

Indeed, given that in every generation more young pureblood wizards and witches take the option of marrying outside the ever-narrowing pureblood sector of the wizarding population, Muggle-born births can be expected to begin routinely outnumbering those of the hard-line purebloods in the foreseeable future, since the numbers of the hard-liners will have decreased.

In the companion essay on estimating wizarding population we can determine that if Rowling’s statements on the current wizarding population of Great Britain and Ireland is to be accepted, the numbers total somewhere in the neighborhood of 3,000–5,000 individuals. Against a Muggle population of roughly 65 million.

At the time that the International Act of Wizarding Secrecy was passed at the end of the 17th century, the population of these islands was roughly 6 million. Which, assuming that the magical representation within the population is generally constant would dictate a magical population of no more than 300–500.

These witches and wizards were probably no more exclusively pureblood than the magical individuals of wizarding Great Britain and Ireland today. Then, as now, most wizards were of mixed ancestry. What is more, to that point they had traditionally lived openly among Muggles and fully interacted socially with their non-magical neighbors. Consequently, when Seclusion was established, those (estimated) 400+ witches and wizards were probably “accompanied” into their secluded world by anything up to 100–250 non-magical family members. Husbands, wives, elderly parents, offspring, and quite possibly siblings, cousins, or other reasonably close extended family members and dependents.

Given that (as Rowling has indicated in interviews) halfblood status is something that wears off after a few generations, by the end of the 18th century most of the infant wizards being born in this “secluded” world would have been some 4–5 generations from their last known Muggle ancestor, and by nearly everyone were regarded as purebloods. We do not know what the population figures for human wizards might have been by that time, but it is unlikely that with so small a base population it would have grown high enough to equal the number of persons the wizarding world had claimed at its establishment when the human “wizarding population” had included the wizards’ Muggle family members. From a bean-counter’s point of view, there would have been a traceable population decline during the period of seclusion.

At that, human wizards were still (even if only barely) the dominant magical race within that world. But it might have looked as if they would not long be able to retain this particular edge without taking some form of action. The fact that Professor Binns sets his 4th years to writing weekly essays on Goblin uprisings that took place over the course of the 18th century is suggestive.

From a base number of, say, 450, if we extrapolate the current pureblood birth rate of approximately 12 births per 1000 over 100 years, (approximately 540 live births) and assume approximately half the infant mortality rate of Muggles at that time (which at that time was close to 50%) we get 405 witches and wizards born after Seclusion was imposed.

Of the original 450 founding magical members of the secluded world, all but a handful would be expected to have succumbed to misadventure or magical malady by that time, as would virtually all of their accompanying Muggle family members. Resulting in 405 plus an undetermined number of surviving wizards over the age of 100. Down from an originally approximated population of 550-700. Add in a double handful or so of possible Muggle-borns from the semi-wizarding villages who had managed to be identified and you still have what appears to be a declining population.


Outside the wizarding world, assuming that the incidence of Muggle-born magical births is anything like that of today, a population of roughly 6 million would have produced perhaps 1 or 2 magical children a year. It is not really possible to make a sound estimate of the survival rate of these children.

Undeveloped and untrained magical conductivity in itself appears to offer no additional health benefits. Where I contend that a trained wizard’s active conducting of magical energies enhances his physical well-being, and may convey a resistance to some Muggle diseases, a magical infant is not a trained wizard and has no such advantage. Nor does an ability to conduct such energies appear to protect one from epidemic diseases, food poisoning or topical infection. Among Muggles in an era without antibiotics, and where infant mortality was near a ratio of 1:1, I suspect that without the advantages of magical healing methods such infants had about as much of a chance to survive as their non-magical counterparts.

Some of these children unquestionably did survive, however, and lived to produce young of their own, perpetuating their magical traits within the mundane gene pool. Over the course of the 18th century the general population rose from 6 million to roughly 11 million, reaching 12 million around 1815. Of which by that time perhaps 75-150 were untrained Muggle-born wizards and witches — and undocumented halfbloods, since many of the surviving Muggle-born’s children will have also been magical. And with the larger population base, the annual birthrate of genuinely Muggle-born magical children of non-magical parents would have risen to 2-4 per year. Every year.

And they and their families, along with their non-magical neighbors were now being forced off the land and into the towns and the factories by the thousands.

Between the years of 1760 and about 1840 over 4,000 Acts of Enclosure were enacted by the British Parliament. At even so small a rate of magical births as 2-4 a year, given that children as young as 4 or 5 were employed in those factories the working conditions would ensure that their involuntary magical breakthroughs would begin to be noticed. And there is only so much of that kind of thing that can be put down to explosions, or mechanical failures.

As much of the wizarding population of Great Britain at this point who could afford to, lived in the secure enclaves such as Diagon Alley in London and possibly other large towns, or in the all-wizarding village of Hogsmeade. The rest were scattered across the countryside, generally in areas without close neighbors, or even more generally clustered in proximity to only a handful of semi-magical villages.

For security’s sake, both the wizarding importers’ consortium (which I propose was formed to supply the needs of the newly secluded wizarding world) and the Ministry of Magic would have actively made it their business to monitor the trends in Muggle society over the previous century. Whereas in the rural communities of the early 18th century a magical breakthrough might pass without a significant number of witnesses, a breakthrough in a factory would be witnessed by many, and it would be talked about. It might have taken the wizarding observers a few years to realize just what was going on, particularly since most of it would have been going on up in the Midlands, rather than in London, but once they did, the matter would have been one of great concern to the people in charge within the Wizengamot. The wizarding world’s continuing secrecy could only be maintained so long as there were no wizards performing magic in the full sight of Muggles. And, obviously, that was no longer the case.


In our own world, the population of Great Britain was to nearly treble over the course of the 19th century. One reason for this is that over the first half of the 1800s the medical profession finally began to get a handle on the problem of infant mortality.

The population of Great Britain reached 12 million around 1815. By the 1850s the mundane population was around 21 million. By 1910 it was some 37 million. It had risen to 49 million by 1945.

If the analogs between our own world and that of the Potterverse remain constant, this would have been reflected with very little variation.

And the birth of Muggle-born magical children has probably also kept pace, with approximately 1 magical birth in about every 80,500.

Or perhaps it has not. That last figure may be a reasonably accurate representation today; but it is likely that since Muggle-born magical children have been routinely identified, trained and absorbed by the wizarding world for at least the last century or two, this figure may not accurately reflect the rates of magical births in the mundane population at the time the Hogwarts quill went into commission.

At that time, any magical child which turned up in the mundane population remained in the mundane population, contributing to further magical births in the following generation. This 2nd generation by wizarding standards would have been halfbloods, not Muggle-borns. And their offspring would have also had a strong predisposition to be magical.

Taking the same, arbitrary total current magical population estimate of 3,250 as was used in the essay above on estimating wizarding population; since around 1800 the pureblood population has increased from an assumed 4?? (which for convenience in calculating we will claim was 425) to approximately 815 today.

Whereas the overall wizarding population has increased nearly 750% from an estimate of 425–450 c. 1800. This increase alone explains the preponderance of wizards and witches who live secretly out in the Muggle world today. I very much doubt that the all-wizarding secluded enclaves could have absorbed any significant building boom to accommodate the increase in the wizarding population. Even if wizards can increase the available space inside a container, for storage or transport, I doubt that they would choose to actually live full-time in such artifically-created spaces.


The pureblood sector of the overall wizarding population’s birthrate is now matched roughly 1:1 by Muggle-born magical births outside the semi-secluded wizarding world. We do not know how long this has been the case. But Rowling informs us that the current demographics at Hogwarts stand at: pureblood; 25%, halfblood; 50% and Muggle-born; 25%. Rowling also implies that these demographics apply to the population of the wizarding world as a whole as well.

Which gives us one of our few potential base numbers upon which to extrapolate just when the Hogwarts quill did go into commission. One quarter of the (ballpark estimate of 3,250) current British wizarding population constitutes 815 individuals. All with projected life spans of 90–120 years. At a rate of 10 individuals per year, it would only take some 81 years for the Muggle-born individuals to increase to that level within the population. However, that rate of 10 individuals per year is generated by a current Muggle population of some 65 million. It has taken a long time for the Muggle-born birth rate to reach its current level.

Of course Rowling does not take this into account at all. Rowling’s Potterverse is a world in which the population never changes and has never been subjected to demographic pressures or imposed change of any sort. But Rowling is not immune to her own cultural context and her vision cannot help but reflect the world in which she actually lives. What we are attempting here is an overlay in which a Potterverse such as Rowling attempts to depict would have developed from an historical context similar to that from which our own world developed.

All such actual calculations, however, are to be taken purely as an artificial exercise.

And as with all such artificial exercises, one does not really ask the question until one has already convinced oneself that one has the answer. I have already identified the period of the early industrial revolution as the time in which external social conditions would have been most likely to make the removal of magical children from mundane society a priority. Would — without making major ovbious adjustments to the available data — a projected increase of Muggle-born magical wizards from that date to the present result in a number roughly that of one-quarter of the modern ww’s population?

Well, let’s just see about that.


In our own world, in 1815, the population of Great Britain was 12 million people.

And at the current rates, and estimating an average projected Muggle lifespan of 60, would have produced perhaps 2 Muggle-born magical children a year.

By the time that Harry was born in 1980, (and by which time an average projected Muggle lifespan was about 80) the Muggle population of Great Britain produced approximately 10 magical children a year.

I cannot think, off the top of my head, of any convincing reason why this increase would have been anything other than more-or-less steady and gradual, although it would have probably seen some peaks and valleys dictated by outside circumstances such as wars or possibly sweeping epidemics.

Therefore, it appears to have taken roughly 165 years for the annual number of Muggle-born births to increase fivefold. This increase has taken place within the mundane population and reflects the increase of a stable percentage of births within the increasing mundane population. Since the magical children so identified have been syphoned off into the magical population, their offspring are not contributing to this increase.

But we cannot be altogether sure of anything. The year 1920 was the year with the highest birth numbers recorded in Great Britain for the whole 20th century, with a total of 1,126,800 recorded births. At the current rate of Muggle-born magical births within Muggle births, that year ought to have produced about 14 Muggle-born magical children. Maybe it did.

The population estimates above give us a little bit more to work from. Assuming an average projected Muggle lifespan of 70 in the year 1910, the Muggle population of 37 million ought to have produced between 6 and 7 Muggle-born Magical children a year.

In the 1850s assuming an average projected Muggle lifespan of, maybe 65, the Muggle population of 21 million ought to have produced 4 Muggle-born children a year.

So; how to calculate the progression.

Well we have no choice but to be arbitrary and artificial.

Estimated Muggle lifespans are included as additional data points. They have little impact upon birthrates, except insofar as they may be indicative of a lowering in infant mortality rates and deaths in childbed.

In the 40 years between 1815 and 1855 the incidence of Muggle-born magical births doubled. 40 years at the 1815 rate would have produced 80 individuals. 40 years at the 1855 rate of magical births would have produced 160. The the mean average between the two would be 120 magical children born between 1815 and 1855.

There are 55 years between our next two checkpoints, 1855 and 1910. In this interval the incidents of Muggle-born magical births went from 4 per year to about 6.5.

In 55 years at a rate of 4 per year the Muggle population would have produced 220 individuals. At a rate of 6.5 per year it would have produced about 358. The midpoint between these two extremes is 289.

Add to this number the 120 individuals who would have been born between 1815 and 1855. 289+120 = 409.

After this point, however we need to begin to factor in mortality rates since the oldest individuals, born around 1815 will be reaching the limits of their projected life spans of 90–120 years.

We have 35 years between 1910 and our next checkpoint, a population of 49 million Muggles by 1945. An average projected Muggle lifespan by that point might have been about 75. By this point (and overlooking possible glitches such as the 1920 baby boom) the Muggle population could be expected to produce 8 magical children per year.

Over 35 years, at the 1910 rate of 6.5 magical children per year, the Muggle population would have produced about 228 Muggle-born magical children. At the 1945 rate of 8 such children per year it would have produced 280. The midpoint of this period would be 254.

Add the previous total of 409+254 = 663. And at this point we need to subtract our original 120, most of whom have reached the end, or are reaching the end of their projected life spans. 663-120 = 543. This is probably an undercount, since it might be supposed that a number of hardy wizards born around 1855 will survive beyond 1945, but they will probably be gone by our next checkpoint of 1980.

In 1980 the rate of Muggle-born births per year was 10.

35 years at the 1945 rate of 8 magical births per year would have produced an additional 280 Muggle-born magical children. At the 1980 rate of 10 per year the Muggle population would have produced 350. Our midpoint is 315. 315+543 = 858.

Factoring in mortalities resulting from accident/misadventure, magical illnesses, and the hostilities of VoldWar I, the actual surviving number of Muggle-born magical individuals may come in at something under the target number of 815, but, at the same birthrate, since 1980 the Muggle population of Great Britain and Ireland would have produced another 175 or so magical children by the end of DHs. So I really do think that we are in something like the right ballpark to postulate that the Hogwarts Quill would have gone into commission at some point between 1815 and, say 1835. It is unnecessary to attempt to estimate the number of surviving Muggle-borns and unidentified halfbloods who may have been alive at our start point of 1815, since it is not to be expected that any of these individuals are still alive today.


The overall wizarding population has most greatly increased within a new and continually expanding sector of halfbloods. (There were almost no halfbloods left in the wizarding population when the Hogwarts quill began recording Muggle-born magical births.) This sector now totals the combined populations of both the pureblood sector and the Muggle-born sector of the wizarding world today. We do not have a definitive description of exactly what portion of Muggle ancestry constitutes a halfblood in Rowling’s wizarding world today, or whether this portion is the same standard that was being applied at the time people started codifying such distinctions.

The society which practiced racial-based slavery in the American south up to the mid-19th century — the period which most closely corresponds to the probable time that the Quill would have gone into commission — defined a person as a Negro who could be proven to have 1/16 “Negro blood”. Which is to trace ancestry back some 4 generations. The 3rd Reich, in Germany in the mid-20th century, in their exercise of attempting to define Judaism as a race, counted back only to grandparents who were members of the “Jewish religious community”, or, a mere 2 generations. (It took nine generations, however, to qualify as a member of their Aryan “master race”.)

For fully half of the wizarding population today to still be counting its descent from Muggle-born “immigrants” suggests to me that the wizarding world traces Muggle descent farther than a mere 2 generations. For that matter we also do not know if there is any formal classification of such anomalies as the children of a Muggle-born couple, who are the offspring of a wizard and a witch but whose grandparents would all be Muggles, or of the magical children of a Muggle-born wizard or witch who might have chosen to marry a Muggle. But at first glance it would seem to be difficult to regard either of these children as being Muggle-borns, themselves.

In any case, the demographics of the halfblood sector of the population would only be tied to the pureblood sector, since without purebloods, there can be no literal halfbloods, and Muggle-born birth numbers outside the wizarding world are largely unrelated to the birth numbers within it. It would seem to be well within the bounds of plausibility that at least half of the (estimated 425) purebloods of around 1800, were the forbearers of the halfbloods of today. Leaving the remaining half, or possibly some segment well below half to have served as the ancestors of today’s remaining purebloods. Not all of whom, as we know, are either supremacists or isolationists. But who do seem to be disproportionately represented among the leaders of the wizarding world, even today. This last is unlikely to continue indefinitely.

If nothing else, the above considerations appear to put paid to the built-in premise underlying the influx of “Marriage Law Challenge fics” which have inundated us over the past decade. It may make for a useful McGuffin for neophyte authors of “arranged marriage” fics (which is a cultural legacy that is inherently scary enough to ensure that some variation of it will probably keep cycling in a wide variety of fandoms. It’s rather like picking at a scab), but clearly any rise in physical/magical/intellectual problems due to excessive inbreeding should only show up within that 25% of the population which has been rigorous in maintaining its pureblood distinction. The wizarding world of Britain as a whole is more genetically diverse now than it has probably been at any point since the International Act of Wizarding Seclusion was passed.


But, given the above; it is easy enough to see just where the pureblood isolationists are coming from; as they see their numbers within the wizarding population being steadily overwhelmed by these apparently endless ranks of Muggle-borns from outside.

But one still has to wonder at just what they think that barring the wizarding world to Muggle-borns is going to accomplish. After all, it’s essentially been tried before. It didn’t work.

True, five-year-olds no longer work 12-15 hour shifts in factories, but they still have magical breakthroughs, and they still grow up to be wizards. And if their magical traits are not siphoned off and put to use within the wizarding world, they will be recycled back into the Muggle population, producing even higher numbers of untrained Muggle-born wizards in successive generations. How do the isolationists expect to be able to maintain a state of wizarding secrecy in the face of that?