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Philip Koop's avatar

In the matter of "how your ideology shows", one could characterize the Fama-French program as "research" or, just as defensibly, "fiddling with model parameters".

I do object to describing a factor model as "explaining" variance in a text intended to be read by the general public. This term is perfectly intelligible - taken for granted - by economists, but is likely to mislead the general reader. And perhaps, subconsciously, it misleads the professional economist too. Suppose, arguendo, that you accept the five FF factors as stable, persistent, and fundamental. The thing to *explain* is why. For example, if value stocks really outperform growth stocks, why is that? An example that has the correct form of an explanation is "value is defined as book-to-market ratio, and there is regression to mean". Another is "the cash flows from value stocks are more evenly distributed than those from growth stocks, therefore they have a higher interest rate convexity". Yet another is "value stocks outperform growth stocks in bad states of the world; therefore the stochastic deflator values them more, ceteris paribus." *Research* would attempt to determine whether and to what degree these explanations are correct. Of course, if the effect is emergent and transient after all, that would be research founded on sand, wouldn't it.

Anyway, "in my factor decomposition of the covariance matrix, factor X accounts for Y% of the total variance" does not have the correct form of an explanation.

Alex Tolley's avatar

'‘Nvidia’s stock has been soaring… pick and shovels… betting on the infrastructure that underlies a new technology…. “There seemed to be a railroad bubble… one a decade after the Civil War,” said Brad DeLong, an economic historian at the University of California, Berkeley. 19th-century investors rightly sensed that railroads were about to revolutionize the economy, and still lost their shirts. But just like the telecom companies that laid internet cables in the 1990s, many of which went bankrupt, the failed railroad companies gifted the economy some helpful plumbing. “In the aftermath of each railroad bubble, we were left with an awful lot of railroads that had been built by investors who had gone bankrupt,”'

I am not clear who the target of this analogy is. The railroad companies went bankrupt, but did the steel manufacturers of the rails? Some telecom companies followed, but did the manufacturers of the fiber optic cable, routers, etc. also go bankrupt? The suppliers of picks and shovels, and other supplies did well during the gold mining booms, but as long as they had other businesses, did they go under? Or did they do well by being middlemen, causing stress on the manufacturers of those supplies when the booms ended?

In the tech industry, some of the big failures were the computer manufacturers - DEC, Silicon Graphics, and Sun Micro, to name just 3. IMO, they failed because they had expensive products that could be replaced by cheaper "good enough" competitors. But the chip makers all seem to have done well and remain active. While Warren Buffett famously said he would never invest in companies requiring fabs as they never created enough free cash flow, TSMC has done very well, and ASML that supplies the lithography equipment remains highly profitable. Intel's fortunes have faded for similar reasons to the computer manufacturers. CISCO did well in the internet boom, but despite leaner times after the dotcom collapse is still doing well.

Is Nvidia like TSMC or Intel/Sun? At this time they have no serious competitors for their technology. Arguably their technology could replace a lot of CPU-based systems in data centers. Their graphics cards are often the most expensive part of any desktop/gaming system. So while they are going gangbusters during the AI boom (with a valuation reflecting it), are they doomed to collapse when the boom eventually slides into the "trough of disillusionment" or will demand for their innate parallel processing approach see steady growth of their chips and systems? As computing resources are now a significant energy sink, technologies that reduce power consumption from ARM chip technology to GPUs is a welcome development.

After a bust, what technology remains useful at firesale prices? Railroad lines were torn up or left rusting, replaced with shiny new roads. It would ne nice to think that all that "dark fiber" is now lit up, but is it? Are all those comsat swarms in LEO going to be useful if SpaceX at al fail to make enough money from subscribers, or will they just be allowed to burn up on reentry without replacement reducing the swarm's capabilties?

IOW, is the basic idea too simplistic and reality far more nuanced, especially when technology is rapidly developing?

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