Ok but global wealth inequality has also decreased specifically because of wage immiseration (mostly as a consequence of outsourcing and foreign investment in China, and south-east India). So again wage growth in formerly poorer countries seems to correlate positively fixed capital growth, rather than inversely correlating.

TRPTF is based on the ratio of variable compared to fixed capital. Fixed capital is machinery and raw materials, and cannot be a source of profit. Variable capital is the labor expended in making a product, and the only source of profit according to Marx (due to exploitation), assuming goods are bought at their true value. The TRPTF occurs when the socially necessary labor time (which is an average that determines exchange value) goes down. So because of faster machinery, it takes half as long to make each t-shirt. When there is less SNLT, the potential profit goes down per tshirt.

If I, or the entire country of Vietnam, takes twice as long to make a t-shirt due to outdated technology (compared to the industry average), I can still only make the socially necessary labor time worth of value, even though I'm working twice as long.

So I'd assume formerly poorer countries (undeveloped) are simple catching up, and becoming developed. They're able to spend only one hour to make a t-shirt, same as everybody else.

As you can see, they've divided TFP in nondurables and durables, and durables pretty closely tracks what Marx meant by "fixed capital". So it's the sectors that are more closely associated with durable goods that have done better, and nondurables that have done worse in terms of productivity. And as it happens it's nondurables (which includes services and hospitality) that have done worse in terms of wages. Is this not the opposite of what Marx predicted? Didn't he say that fixed capital intensive sectors would be the ones who saw their wages stagnate? Instead it's the jobs in the "fixed capital" sectors that have seen the best wage trajectories.

https://www.investopedia.com/terms/s/service-sector.asp

Trying to get a better definition of "service sector" it appears as if the service sector is actually quite reliant on technology.

Technology, specifically information technology systems, is shaping the way businesses in the service sector operate. Businesses in this sector are rapidly placing more focus on what is becoming known as the knowledge economy, or the ability to surpass competitors by understanding what target customers want and need, and operate in a way that meets those wants and needs quickly with minimal cost. In nearly all industries within the sector, businesses adopt new technology to bolster production, increase speed and efficiency, and cut down on the number of employees required for operation. This cuts down on costs and improves incoming revenue streams.

I would think that with the internet and other advances, the service sector has probably seen much more improvements in efficiency (lowering of SNLP) than other industries like durable goods. Account information isn't on file, someone scans something and it is done. GPS finds the quickest route in transportation. Healthcare information is readily on file, without a secretary making calls, sending mail, or fax. Your taxi gig goes to your phone. Your amazon warehouse worker application makes finding the item quicker. Increased computer technology has made call center, information, entertainment, all much more efficient in terms of speed.

Of course, without a fungible good, I'm also not sure service center jobs always apply in Marx's understanding.