[engi_nerd]

Okay, I'll play devil's advocate here.

There's a huge (but not insurmountable) lock-in effect behind wire gauges. All the wire I can buy is sized in it. All the wire strippers, crimpers, pins, sockets, plugs, jacks, terminal strips, insert/removal tools and clamps I can buy are sized around the AWG standards. Bulkhead passages in ships and aircraft are sized for carrying certain numbers of wires of certain gauges in bundles. Tens of millions of engineering drawings specify wire sizes in AWG.

So why should we in the US change all of this? Just for the sake of being "modern"? I'll need a more persuasive argument than that.

[VLM]

A somewhat more interesting problem is we live in a centrally controlled economy with many centers. There's a paperwork storm downstream of thousands of local building codes. Most are minor variations on minor details of the NEC, but it would be a huge job to harmonize and metric-ify them. For example where I live, politicians "had to do something" after someone died in a pool electrocution decades ago, so our local code is NEC plus a microscopic tightening of 1950s NEC swimming pool regs (which ironically are probably looser than 2016 NEC swimming pool regs, negating the politicians intent from decades ago).

Anyway at least for awhile if you want legal electrical work done, you're going to have an incredibly expensive and dangerous cutover. Its likely that cutover to metric related mistakes will cause as much property damage and death as "X" years of not harmonizing under one system. Where "X" is probably many more years (lifetimes?) than you'd expect.

[engi_nerd]

And that's just the economic "center" for commercial and residential structures. There are centers in lots of other industries. I referred to the one that I deal with directly (fighter aircraft) in my original post. I'm sure you've thought about multiplying this effort across hundreds of other industries...

[rm445]

Yes, that's the core of the issue. The US is a big monobloc, an economic superpower with not only the most advanced economy but also a lot of the history tied to developing the world's industries.

Other places saw more benefit to adopting SI units either because they were smaller and closer to lots of other places with a need to harmonise, or playing catch-up. My own country, Britain, falls in the first group - though the population still uses some everyday old units, it didn't manage to be a hold-out despite its historic position and industrial heritage.

It's hard to see the position being static in the longer term though, particularly if world economic growth gradually leaves the USA with a relatively smaller slice (in absolute terms much bigger, but a smaller proportion) of the larger future world economy.

[engi_nerd]

I agree. The only way things in the US will change with regards to standards like this will be if it becomes excruciatingly painful to continue being different.