High taxation is important and so is inflation of the currency and the ratio of the productive to those on the public payroll. But that's old hat; everybody knows that a country is on the skids when its income and outgo get out of balance and stay that way - even though there are always endless attempts to wish it away by legislation. But I started looking for little signs and what some call silly-season symptoms.
I want to mention one of the obvious symptoms: Violence. Muggings. Sniping. Arson. Bombing. Terrorism of any sort. Riots of course - but I suspect that little incidents of violence, pecking way at people day after day, damage a culture even more than riots that flare up and then die down. Oh, conscription and slavery and arbitrary compulsion of all sorts and imprisonment without bail and without speedy trial - but those things are obvious; all the histories list them.
I think you have missed the most alarming symptom of all. This one I shall tell you. But go back and search for it. Examine it. Sick cultures show a complex of symptoms as you have named... But a dying culture invariably exhibits personal rudeness. Bad manners. Lack of consideration for others in minor matters. A loss of politeness, of gentle manners, is more significant than a riot.
This symptom is especially serious in that an individual displaying it never thinks of it as a sign of ill health but as proof of his/her strength. Look for it. Study it. It is too late to save this culture - this worldwide culture, not just the freak show here in California. Therefore we must now prepare the monasteries for the coming Dark Age. Electronic records are too fragile; we must again have books, of stable inks and resistant paper."
-- Robert Heinlein (Friday, 1982)
......which segways nicely into.....
“Be courteous to all, but intimate with few, and let those few be well tried before you give them your confidence. True friendship is a plant of slow growth, and must undergo and withstand the shocks of adversity before it is entitled to appellation. ”
-- George Washington