So why exactly does almost ALL tech live in Silicon Valley?

I'm sorry, but some assumptions are wrong

First of all Silicon Valley isn't about technology of knowledge. Silicon Valley today is mostly about business trying to sell advertisements If any company has a small development branch, it's just there to help sell those. That's why there is next to no innovation in our world today. That's why Ubuntu Phone is near indistinguishable from Android or iOS.

Then second, the amount of money you get doesn't depend on how much you know, it depends on where you work. And well paying jobs in engineering are usually not the better ones. And even the highest paying jobs in engineering don't even pay a fraction of what even proven to be incompetent upper management people get.

Without really good education there is simply no market for technology. Why should someone buy the device that's better engineered when they don't understand what's better about it?

"And despite the steel works being gone for decades non-ferrous metals trades still set up around Sheffield and Rotherham."

I think you mean ferrous metals. And Sheffield & Rotherham produce more steel than ever, it's just that nowadays it only needs one man and a dog to do it. The man to feed the dog, and the dog...

A Zombie concept?

"Firms in the same trade end up setting up alongside each other simply because it's more convenient to do so. That's where all the skilled workers you're going to poach are, after all."

The corollary of that being that that's where all the firms who are going to poach all your skilled workers are so you have to get together with them to set up anti-poaching agreements.

Where physical work is concerned there may still be a rationale for clustering. If you have a non-ferrous metalwork plant you need to be in a place where there's a concentration of skilled staff to operate it and conversely if you're a skilled operator you need to be in a place where there are firms with plant needing operators. But where the plant is mostly laptops that the skilled staff can afford to own and a server which can be located anywhere & rented then "where" resolves to "any place with an internet connection".

The consequence is that a dispersed workforce has demonstrated the ability to collaborate produce major operating systems and other substantial S/W. Maybe for many types of creative work the clustering concept is already dead, it just hasn't lain down yet.

another element which leads towards clustering is the local authorities views on planning: whether historically they were prepared to accept hazardous processes, environmental issues, etc.

Thats why historically you had clusters of butchers shops in towns, often known as the "shambles". Keeping the butchers together kept the animals wastes together. On a larger scale, there was a tendancy to group trades such as leathermaking together - usually near a source of water into which waste could be poured. Steelmaking tended to be clustered because thats where the fuel was - initially charcoal, later coal/coke. It was easier to transport the iron ore that it was to shift the bulky charcoal fuel (until the arrival of the railways). But you have to consider second/third technology generation effects as well......why did you get so many IT manufacturing companies setting up in the Clyde area in the 1970's? Because there was a large pool of unemployed labour there of people who could be retrained. People who had proved to be skilled in one job, now redundant, but intelligent enough to be successfully reskilled. None of the "new" Japanese owned UK car plants were in traditional car-building towns. Think Swindon, Derby, Hartlepool, but all had a tradition of skilled engineers who could be retrained. Ironically one of the biggest pools of available labour for the Clyde IT plants was due to the closure of the Linwood Hillman Imp plant

Another fact is.....spinoffs from local centres of Academic Excellence. All you have to do is cruise around Cambridge in a 15 mile circle and count the number of high-tech chemical/biochemical/drug discovery/electronic/IT businesses which have spun off from projects at Cambridge University. Hundreds if not thousands. The key deciding factor there is closeness to the university, easy access to other academics for mutual support.

In short, clustering of businesses isn't such a simple art as you imply

On the other hand...

Isn't part of it simply to have a business address there so you get reputational points?

Simple answer, really.

Post WWII, people from all over the world attended Berkeley and Stanford. They discovered that what became Silly Con Valley was a nice place to live, and upon graduation, stayed here.

This lead to the plowing under of the orchards to create a new suburbia to house the large quantity of educated people.

In essence, an educated melting-pot made this place what it is.

Personally, I miss the cherries, plums, apricots, peaches, etc. ...

Another question

If birds of a feather, flock together, then would a few cluster bombs in Dallas sort out the troll problem for good?

People move their tech businesses to Silicon Valley because...

Of the low price of real estate...well, no, that's not it.

Because there isn't much traffic....well, not that either

Well, the weather is great!

(More seriously, it's an ongoing network of tech-literate professionals who keep engendering new projects, that require more tech-literate professionals, who engender more new projects, and so on. All this started in the beginning because of HP, and the fact that William Shockley moved his transistor/semiconductor research/business from New Jersey to the Santa Clara Valley to be near his sick mom who lived in Palo Alto. That begat Fairchild Semiconductor, which begat the "Fairchildren", the most notable of which were Intel and AMD--and from there it was off to the races.)

P.P.S.--there's a great "American Experience" episode titled "Silicon Valley". Well worth watching if those of you who live overseas can find Public Broadcasting Service programming.

What is tech, anyway?

Before Silicon Valley got known as such the centers of computing technology used to be in places like Chicago and Minneapolis. The axis shifted to the Bay Area because of universities like Stamford doing pioneering work in microelectronics. This then morphed through early PCs into networking companies and finally to companies that built software based on the PC/networking infrastructure. The technology, though, is everywhere, not just in this one area. Its just that to participate in this work you need a whole lot more knowledge than just being able to code in the language-du-jour.

"why the nerds get paid so damn much"

Simple, when rent is $2500+ a month and house prices are $600000 and up, you will have a hard time getting by with less than $60000 a year. Not forgetting the other higher costs of living.

IT workers here don't get paid that much more, considering. The idea that IT wages is sky high in silicon Valley is flawed and misguided. You'd be lucky to be offered more than $70000 a year as a mid level IT person/programmer, with, say, 2 years experience, let alone fresh out of college (good luck getting a job that's more than a crappy underpaid intern position, experience is everything).

And lots of companies like to hire foreign workers who they can pay considerably less, because they depend on their employer (H1B1 visa abuse).

Start ups frequently dare to advertise vacancies where the pay is a minimal stipend, with the lure of stock options and a questionable future fortune to be acquired (95%+ of startups fail...). And even if you happen to earn a decent wages you have (or are expected) to work more than 40 hours a week, which renders that wages on an hourly basis quite low.

The only IT workers making a fortune are those who happened to be lucky (not merit really) enough to own stock options in companies that subsequently grew a lot, or were bought by larger companies. For the other 99% of IT workers here it's the same old grind as anywhere else.

At least it's sunny with stunning nature at your doorstep (if you like sun, it starts to get to me...).