This will be my least-read blog post. 

In George R. R. Martin’s Fire and Blood, a history of the Targaryen dynasty, one little line always stuck out to me. It concerns the success of King Jaehaerys, who ruled Westeros for fifty-five years.

Archmaesters can and do quibble about the numbers, but most agree that the population of Westeros north of Dorne doubled during the Conciliator’s [Jaehaerys’s] reign, whilst the population of King’s Landing increased fourfold.

Now, King Jaehaerys is described in Fire and Blood as a great king. He stabilized the realm after years of warfare, built roads, modernized the capital city of King’s Landing, and generally presided over more than half a century of peace and prosperity. However, let’s examine that population growth number. 

Going through the math, for a population to double in 55 years, it needs growth of almost exactly 1.3% per year. One point three percent population growth may not sound like a lot, but it is.  Let’s go through some historical comparisons to show just how insane that number is. 

Of all premodern (pre-1500 or so) history, there are very few cases of rapid, sustained population growth in a continent-sized area. Probably the most dramatic instance is Europe during the High Middle Ages (1000-1300). During these three centuries, the population of Europe doubled, as incredible feat considering how in the centuries before and after the population remained more or less stable.  

The period had many similarities to the reign of King Jaehaerys. Warfare became less common, peasants gained autonomy, and infrastructure improved. Because of these developments, Europe was able to grow at a rate of 0.23% per year. That’s right. The most impressive protracted population growth in all pre-modern history was less than one-fifth of the population growth achieved under the apparently superhuman King Jaehaerys. 

Another possible comparison would be Japan during the 1600s. During that century, Japan was almost completely isolated, and recovering from the violent and anarchic Sengoku Jidai period. Between 1600 and 1700, the Japanese population more than doubled, a rate of almost 1% per year. Yet even this was well below Jaehaerys, despite involving far more advanced agricultural technology than is present in Westeros. 

As time passed, agriculture (especially fertilizer) and globalization enabled still faster growth. In a 61-year period between the 18th and 19th centuries, China’s population doubled, a rate of 1.14% per year. Europe achieved a similar feat between 1871 to 1914, growing from 293 million to 490 million, a rate of 1.2% per year. 

Things changed even dramatically with the 20th century world. Today, countries can import huge quantities of food, access advanced farming techniques, and enjoy far improved medical care. That has allowed several 20th century regions to, at last, exceed the growth of  Westeros under Jaehaerys. Between 1950 and 2000, Africa achieved a population growth of 2.26% per year. Latin American growth was almost as high. China’s population also exploded in the fifty-five years between 1955 and 2010, but even that meant a rate of just 1.26% per year, barely higher than Jaehaerys. 

So while the type of population growth described in Fire and Blood can theoretically happen, it requires a perfect combination of modern technology, disruptive social change, outside input, and centralized political control. None of those things are present in the stagnant world of Westeros. 

In the grand universe GRRM has created, it may seem hyperbolic to call the Westerosi Population Explosion the biggest world building mistake. After all, 95% of his readers have never even heard of King Jaehaerys. 

But in all Westeros, nothing is as blatantly wrong as the population growth under Jaehaerys. Absurdly immense architectural features like the Wall or the Eyrie can be justified by their grand aesthetics, or even explained away by popular fan theories involving long-vanished advanced technology. Fantasy elements like dragons and magic are… well, magic. But there’s no magic or crazy fan theories that can explain a 100% growth in population over 55 years. It’s just sloppy storytelling. 

[End rant]