Rome fell in 476 AD, according to the high school and World History 101 shorthand we are used to. You can prefer a date in the 370's instead, or 410, or the Vandals taking Carthage in 439 AD, which broke the tax spine of the Western Empire for good. Going in the other direction, you can choose the collapse of the reconquest by Justinian in the late 6th C, or even later. If one wants to be really technical, Constantinople, the Eastern capital of the Roman Empire for a thousand years after Rome itself fell to Ostrogoths, did not fall until 1453. Few would pick that date, but you could, and make an argument with at least some facts to buttress it.
But let's focus on 476 and let that hover in the background as we look at the collapse. In 440AD all looked bleak for the empire, though those in the central cities did not perceive it. Britain and Northern Gaul had fallen out of the empire. Northern Africa was a trading partner, not part of the empire. The influence over Persia, Syria, and the easternmost sections of empire was waning. Yet by 450, trading was bustling again. Some researchers would claim that this was actually the height of trade throughout the Mediterranean, unmatched for more than a thousand years. There was recovery! Despite all the dark portents, Rome reached its height. Arguably. Some would pick 150, 350, or other dates. Still, a case could be made.
If you were living at the time, those naysayers who pointed to the loss of tax revenue from across the Mediterranean, or the growing power of the Goths, who had an internal kingdom in Gaul, or the slow loss of border provinces and increase in cross-border raiding would be laughed off. However plausible their arguments might sound that the empire was in decline, the objective evidence was that things were fine.
Just ten years later. 440AD to 450AD. They didn't know it, but the collapse was indeed near, because long-term secular trends were overwhelming short-term local ones.
I think of this when I read Andrew Yang's worries about the coming jobs catastrophe. He believes that automation is going to destroy more jobs than it creates. Note that he is not a typical doomsayer. He does understand that jobs will be created as well as destroyed. He thinks the latter will be greater.* Truck drivers and cashiers are on the near horizon of disappearing jobs. There are millions of those. The jobs created in a new economy will have to be very impressive to keep up with that over the next three decades.
He was honest with Democrats that job retraining mostly doesn't work. Republicans didn't notice this courage, Democrats generally just whistled past the graveyard.
The traditional argument against this is powerful. I have seen Texan99 make it several times. Despite the impression we always have on this side of the divide that more jobs will be lost, the consistent experience of humankind is that there are actually more jobs when we get there. There are fewer jobs for buggy-whip makers and manure-shovelers, but lots and lots of automotive jobs. That might be the way to bet. However, I am reminded of Nicholas Nassim Taleb's description of the Lebanese who believed that after a thousand years of Christians and Muslims living together, the 20th C difficulties would end the same way. So they moved to Cyprus decades ago to wait out the temporary antagonism, staying in hotels there.
They are still in hotels in Cyprus.
I don't take on faith that there are other jobs that will show up as Amazon automates delivery, both in the warehouse and on the highways. I'd like to think there are other jobs for the low-skilled working at $8-12.hr in convenience stores. Such jobs have appeared before. Yet I don't see any guarantee of that. The past is the best predictor of the future, but it is not an infallible predictor of the future.
Things look great at the moment, and in the short term I think that can hold. Will it hold two more decades? Four? What will we do with decent people who would absolutely show up on time and work hard, but there are now ten of them for every four jobs?
*Relatedly, when he touts Universal Basic Income, he does not pretend that there is no risk and no loss of productivity, as most hemp-headed advocates do. He believes that it is a 70-30, or perhaps only 60-40 tradeoff to give more freedom to the poor. If you dig deeper, he believes that some percentage (I conclude from his comments about 50%) of the poor are generally hardworking Americans, who don't have a lot of skills or whose industries collapsed or had bad luck, who would do fine with a minimal safety net. Those, he thinks will muddle through with just a little help. He hints that there may be a lot of minorities in this group, who would be better served by supplement rather than rescue, and would generally not take advantage.