I read it a little differently: 1920-1940, just 20 years, including 12 years of The Great Depression, saw just explosive growth in telephones, electric power, electric motors, electric lighting, radio, autos, oil, steamships, chemical engineering, and airplanes with continued growth in railroads and, thus, steel, Great Lakes shipping, and more. Then could go to college and study 'industrial arts' with chemistry, strength of materials, metal working, wood working, printing, etc. with excitement much like studying computer science in college today. My explanation: Small gumment, meager regulation, big bucks left over from the Gay 90s available for investment.

Then 1940-1970 the US DoD kept giving high technology many really big kicks in the back side to move much faster each year. That's what built Silicon Valley, much of Boston, several labs around the country, and many labs around DC.

But, the war in Viet Nam and the subsequent mess of the inflated economy, e.g., the 22% prime rate and the S&L crisis, and the oil shock of 1973-4 slowed things down through at least 1980.

But in 1980, IBM retreated from their grand 'future systems' direction and did another turn on the 370 architecture and started selling 370s again. They were shipping from their plant in Kingston, NY. The 18 wheel trucks that came to pick up the boxes got in a queue starting a the plant and continued out of Kingston and onto the NY State Thruway and formed a queue there. There was a blip in the GDP. So, things were starting to grow again.

By 1990, IBM was starting to hurt; microprocessors were taking a big toll on IBM's revenue. In three years near 1994, IBM lost $16 billion and went from 407,000 employees down to 209,000 and cleared out rush hour traffic jams in several counties north of NYC.

Since then we've had the dot-com bubble, 9/11, two wars of 10 years each, the housing bubble and The Great Recession, the end of the Cold War, the end of much of the Space Race, and, thus, no longer big Federal bucks for 'aerospace'. So, some things slowed down.

This should be a time of explosive growth, especially exploiting the price/performance of current computing and optical fiber along with the infrastructure software. To do what? Sure, to automate as much as possible of everything there is to do -- computers managed by computers ... managed by computers several levels deep managed by humans.

But there is a big financing problem: The big, old companies don't like to innovate, are not being pushed by DoD and NASA, and don't see the big profits that IBM long did. So, innovation is up to small companies. Alas, the way the financing works, really there is essentially no funding for the research and early development anything like what gave us everything from the electric light bulb through the electric typewriter, the nuclear power reactors, the Xerox machine, System 360, the SR-71, Multics, DEC VAX, AT&T Unix, and more.

So, now the IT R&D is from 1-3 guys funded by personal checkbooks. The 'professional' money doesn't want to get involved until all the R&D is done, the product has launched, and there is significant 'traction' growing rapidly. That's a long way from, as I recall, Rockefeller writing checks to get Edison and/or GE going so that we could have electric lighting instead of gas lighting. And if Rockefeller asked Edison how the bulb was going, Edison could only say that he knew 1000 things that wouldn't work.

And the ability to raise money on the stock market is much less good: 100 years or so ago, could form a company on Monday, print stock on Tuesday, sell it to the public on Wednesday, and then by Friday be building the new steamship, railroad, hotel, coal mine, or whatever.

Currently Apple, Google, Cisco, Microsoft and more are sitting big piles of cash and should be able to fund a next big thing like Rockefeller funded electric lighting.