Disclaimer: This has been something I've been thinking about since long, long before November, and have been working towards for multiple years, with a major move and life change a year or so ago related to it - so, let's try to avoid politics, because who the captain is doesn't matter that much if the ship is sinking.
Nations rise and fall - we see this throughout history. Generally, a nation will last hundreds of years before falling down the dustbin of history into irrelevance, and nations that strive for stability over all else can last thousands.
If one assumes the average age of nations is a few hundred years, and that most humans will live to 60-80 years, that lifespan will cover a good chunk of a nation's life. We're not that many human lifetimes away from the founding of the United States or many of the countries over in Europe.
And if one is making plans for, ideally, 30-60 years in the future (as many people here are), considering where a nation is on the arc through history is worth spending a bit of time on.
I'm generally of the opinion that the US is somewhat past our peak of our run, with a peak probably in the 60s or 70s. A number of important metrics have been going down since then, but the exact dates don't matter that much. If we are 25 years or 45 years past peak, that doesn't matter as much as the fact that we are past peak and, over our expected lifespans and retirement, will be in a nation that's heading further downhill.
So... starting with the assumption that the US (which is where I live) is a nation in decline, at some point past the peak of our arc, what are reasonable things to consider going forward, and how are you working those out? I'm in my mid-30s, hope to live well past 70, and would like to cut back on work going forward, though I doubt I'll ever entirely retire - my projects do tend to generate income after a while.
I'd start by offering that I don't think the markets are going to be reliably going up for another 35+ years. There are simply too many headwinds against continued exponential growth on a finite planet to rely on this. The current economic systems are quite addicted to growth, and lots of things just fall apart if they don't get it. If you're looking out 10-15 years - you might be fine, but longer? Eh. Growth is a risky gamble to make for another 40-50 years.
On top of that, nations in decline tend to do a poor job maintaining their infrastructure. There's just no money to do it, and "Eh, I'm sure the roads will be fine for another year..." eventually turns into gravel roads where you once had pavement. Not that as many people can afford fancy cars to drive on them anyway.
And things just generally don't work as well. That which you relied on becomes unreliable, then goes away. That which was certain becomes less certain. And, historically, political polarization keeps increasing, and governments become less and less functional, and eventually fade out of the picture entirely (except, usually, for taxes - they'll happily demand money for services they no longer provide). This is more true for large governments (national) and a bit less true for local governments.
Finally, as nations wind down, they tend to either get overrun from the outside, or fragment into regional nation-states. Personally, I'm betting on the second. I think there's a decent chance I'll see it in my lifetime, but I'm by no means certain on that point.
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That said: How do you go about designing for these potential futures, while not missing out terribly in the event that we can keep kicking the can for another century or so and not face the consequences?
I'd offer that, from my point of view, the best way to deal with this is to live a good bit below your means, gain useful skills in areas that seem important going forward, and work towards reducing your long term expenses as much as you possibly can while providing for your needs - and, if you have the space, look towards being able to provide a surplus to help your local community.
FIRE types are usually well set as far as living below your means goes - that's sort of how you get to that point in the first place. If you're not on the edge financially, you can absorb a lot of shocks and be totally fine. So that's not a problem. I would offer that focusing on lower tech entertainment is probably useful. Board games will last a long time. XStations? Meh.
Skills is an interesting area that, in my view, is worth a bit of a gamble. If you're on the FIRE path, and especially as you transition out of work with a good chunk of wealth saved up, you can afford some gambles on "weird" skills. Gardens, machining, making furniture - if things keep going up, great. You've got a fun hobby. But if the markets refuse to behave, you have some useful and, ideally, lower tech level skills you can fall back on. Knowing the details of dense gardening in your local soil is of value. Being able to build and repair things of value (including building parts for machinery and cars - that may be in demand). Things like that. Or even just being a good storyteller.
As far as expense reduction goes, this is one that's probably the most controversial, at least on this forum - but I think it's also one of the most important. I've been working towards investing in productive property improvements that will reduce my long term expenses, even at the cost of spending more money now.
Solar is a good example. The common way of doing solar right now is grid tied, with micro-inverters. This is perfectly fine, as long as the power grid is reliable (and power companies let you use the grid as a free battery). Most of the microinverters on the market, as installed, will not function without the power grid. If we're heading into a future where infrastructure is less reliable each year, this is a problem.
An alternate way of doing solar is with inverters and a battery pack designed to run at least a set of critical loads (which, depending on your house, may be most of it) without the grid attached. It's more expensive up front, but gives you the ability to keep the lights on if the grid, locally, becomes unreliable. Or, more tactically, not keep the lights on, but keep the fridge and freezer on, the well pump running, etc. Lead may not be the best battery tech here. Nickel iron is inefficient, but long lasting, and some of the more boring lithium chemistries are pretty long lived as well.
If all goes well, you pay for your power bill going forward. If all doesn't go well, you still have refrigeration in the summer when things are hot, and, well, if it's cold and dark outside, putting things outside will keep them nicely cold.
Another area worth looking at is food production. My goal, mid term (5 years?), is to be able to feed my family (which includes grandparents) from our property. This is a special challenge here because I live on a pile of basalt with alkaline soil. But, I'm planning on trucking in some decent soil, working with compost, and working towards an aquaponics greenhouse (growing fish and plants in a synthetic pond ecosystem). It's a good bit of work, but it's interesting, useful knowledge (see skills, above), and I'll have an idea as to where my food is grown. It's hyper-local, and if things go well, I have plenty of surplus for a local gift economy, and if things don't go as well, I'm ahead of the curve in terms of knowledge and equipment.
Finally, at least for me, I've been working on my small electronics repair knowledge, and building local systems that don't rely on the internet and cloud to function. There's just no reason I need a cloud based watering system - and I'd rather have one I designed and can maintain.
I'm also working with electric bikes, both in terms of repair and design, because they're a wonderfully cheap car replacement. If things go forward exponentially, I have a neat hobby, and if things don't, I'm ahead of the curve in terms of understanding a great, wonderfully cheap, solar-chargeable replacement for cars.
My overall goal here is to hedge some of the risks of things not going as hoped. I'm certainly putting money in the markets and index funds, but at the same time, if I have a productive property improvement I can get long term return on, I'll put money there over the markets. And I do keep some value stored not in USD.
I openly admit that this is not the most "efficient" way towards FIRE. But it does seem reasonably robust against some of the risks that things might not go as hoped. If things go great, I have a very low cost of living and money coming in from the markets and I can do whatever I want. But if things go less-than-great (which, again, looking forward 40-50 years, I see as highly likely), I think I'll be better set, and ideally will have the resources to be useful and generous in my local community, which is what will matter.
Thoughts?