Tomas Pueyo Profile picture
Apr 5 18 tweets 7 min read Twitter logo Read on Twitter
The Texas Triangle , between Houston, Dallas, and San Antonio, contains 75% of Texans.

What's special about that triangle? Image
A map of night lights shows that ppl are concentrated in its tips and edge:
• One of its tips is the massive Houston
• Another tip is an uncommon type of city: the couple Dallas–Fort Worth
• Then there's a line of cities between Dallas and San Antonio w/ Austin, Waco...
Why? Image
What can the satellite tell us?

If you look carefully, you can see a green and grey line running from San Antonio to Dallas. What is it? Image
The topography can give is a clue: the mountains drop in altitude on a line from San Antonio to Dallas! This fall line transforms the mountains into hills that can be crossed Image
Sure enough, many of the most important Texan cities are on the fall line of the Edwards Plateau. These form the grey line on the satellite picture.

But why did these cities emerge at these points on that line, and not others? Image
They're each at the crossing between that fall line and a river:
• San Antonio: San Antonio River
• Austin: Colorado River
• Waco: Brazos River
• Fort Worth and Dallas: Trinity River
This is the same as on the Atlantic Seaboard Image
And like on the Atlantic Seaboard, there's a road connecting all these Texan cities: the interstate 35.

The enduring value of this route is revealed in its ancient origins, as this very path is probably the same as the ancient Chisholm Cattle Trail

We'll get back to it Image
The pbm with these rivers is that they're not very navigable. They did bring water and irrigation to their cities—hence why they appeared there—but their transportation utility was limited. Which is why Texas pushed hard to develop its railroads. Image
The end of the 19th century saw both a huge construction of railroads and the discovery of oil. Both of these finally started the growth of the Texan population Image
So that's why one edge of the Texas Triangle is so populated. But why is the other tip in Houston? Why not anywhere else on the coast? There are plenty of other successful ports in Texas, even to this day Image
Normally, you just have one big port per region, because there's benefits in having all the goods go to the same hub.

And natural bays tend to be the place where they emerge, protected from the ocean. But there are several bays in Texas. Why did Houston's bay win? Image
It didn't

In the 1800s, Houston was not the biggest port in Texas. It was Galveston, established by the Mexicans in 1825

Galveston grew because of its position:
• Great bay
• Close to N Orleans
• As close as possible to the other main TX cities: San Antonio, Dallas, Austin.. Image
And then in 1900, Galveston learned a lesson that other regions had learned through centuries of storms: Galveston was too close to the sea.

It suffered a hurricane that devastated it. The port and industries moved as inland as they could.

That was Houston. Image
Houston was at the confluence of two navigable bayous, had invested in improving their navigability, and had received one of the earliest railroads on their way to Galveston. It had all the infra it needed and was close to Galveston. Perfect heir.

Hard for other ports to compete Image
So that's why 75% of Texans live in the Triangle:
1. End of the Edwards Plateau
➡️easier transportation
➡️rivers form
➡️great spot for cities, which follow the fall line: San Antonio, Austin, Waco, Killeen, Fort Worth, Dallas

2. Houston, heir to well-located Galveston Image
I write threads like this once a week. Here, on California. Follow for more

I'll write soon about why New York is the biggest city on the Atlantic coast.
This doesn't explain why Dallas and Fort Worth are so close to each other. I'll write about this in my upcoming article on this.

And maybe about other cities: Pittsburgh, Minneapolis–St Paul, Kansas City.. Sign up to my free newsletter to receive it
Some of you mention rainfall. True: there's more rain east of the line—because altitude is lower! We can see the line in the precipitation maps of spring: a rain line passes through the fall line (left)

But it disappears during late summer rainfall times (right) ImageImage

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More from @tomaspueyo

Mar 31
Why is LA California's biggest city?
Why is the state's capital Sacramento, only the 7th biggest city?
Why is SF so important despite being on hills?
Why did San Jose pass it in population?
What's the role of the Central Valley?

How to understand California:
Los Angeles is more than 2x more populous than the SF Bay Area, which in turn is more than 2x San Diego's. Sacramento is the 4th metropolitan area and 7th city by population.

So why is it the capital?
This was not the population distribution 170 years ago, when California became a US state.

If you look at the most populous counties then, you might not even recognize 3 of the top 5. Why?
Read 27 tweets
Mar 29
Will AI lead to economic disruption?

My friend @Noahpinion believes that, so far, we can't see the impact of automation on economic statistics. I think we can. You just need to know where to look

Let's dive into:
1. Unemployment
He argues the right way to look at it is the share of 25-54yo employed

But it has shrunk
And much more if you just look at men
Of course! Females have been joining the workforce—a huge win
And there are many more confounding factors: more education also lowers labor rates for males, there's also immigration, globalization, urbanization, health...

With all these confounders, it's hard to tell what caused what.
But prime-age labor in male has dropped
Read 25 tweets
Mar 21
Is your job at risk? When will it be replaced by AI?

Here's how you can tell, with examples of industries like movies, law, education, logistics, construction, and more:
The recent and sudden improvement in AIs like LLMs is scary: many of them are better than *specialized humans*. Eg, GPT-4 is better than 90% of *candidates passing the bar*
New papers suggest that these technologies spell danger for telemarketers, teachers, lawyers, psychologists, mathematicians, accountants, proofreaders, assistants………
Read 28 tweets
Mar 18
What's the biggest Mississippi city?

Why? Because of an ice age water stream

If you understand this, you can understand why Chicago is so huge today

And more importantly, why some cities thrive while others don't:
This is the Mississippi Water Basin. There's something weird. Can you see it? It touches the Great Lakes! How is that possible? Does water flow from the Great Lakes down the Mississippi? No! Then?
Look how close it is! The Des Plaines River, a tributary of *the Mississippi*, flows through Chicago, and is about 10 miles away from Lake Michigan!

A slight difference in geology could have made the Great Lakes flow into the Mississippi.

In fact, they used to!
Read 23 tweets
Mar 14
GPT-4 passes most intellectual tests better than most humans

This will make the world much more productive. But also replace many jobs. Replacing many is just a matter of deployment

If you’re not scared about its abilities today, you should worry about its trajectory Image
Here’s the improvement compared to GPT-3.5
Look at those green bars!
In 6 months! Image
Here’s the research site
Sign up for the waitlist if you want to try it
Read 4 tweets
Mar 4
The debate on whether masks work continues. As I've dived further into it and received feedback, I've updated my views

Here's the detail of the original thread

And then I added much more color here…

Here are the updated views:
As a reminder, all the debate is around the Jefferson et al. Cochrane study, which you can find here…

And tackles articles like the one from the NYT, which used the NYT article to claim that mask mandates don't work…
1. The articles interpreting the paper as saying "mask mandates don't work" are still complete rubbish.

You can expect that from journalists.

What's still surprising is how much the quotes from the lead author don't reflect at all the findings of the study:
Read 25 tweets

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