I'd often been curious about whether there was a generational tipping point in colonial America that led the colonists to seek separation. In other words: was it just that by the 1770s, there were enough native-born Americans that at some point they were going to stop feeling close kinship with the mother country, and would find some flashpoint to use as a case for separation, taxes or otherwise? This is attractive because it gives us a number and can be simply modeled; you could see where a colony is on the "revolution curve".
A case is often made that after the Seven Years War, the colonies began to view themselves as able to defend themselves, while resenting restrictions the Crown placed on territorial expansion. Once this change in perspective occurred, along with a land-owning elite that had been reading a lot of Enlightenment books, the clock was ticking. Is that it? Or was the clock ticking because of basic demographic factors?
The answer is: not obviously. In 1790 the proportion of immigrants in the colonies was, at absolute most, 24% of the total population. (This simple data is mostly from Wikipedia.) English immigrants, who might be more loyal to the Crown, not even 6% were born in England (if you include the rest of the British Isles, that comes up to 11%.) In fact, the actual numbers of people born outside the colonies must be much lower than this, since this number assumes that everyone who ever immigrated to the colonies was still alive in 1790, which is obviously nonsense, and immigration slowed down around the time of the Seven Years War. So, if there is a native:homeland ratio serving as a "demographic trigger" for separation, it's well below one-quarter and maybe even around 10%.
You might be thinking, "the colonists must have felt completely separate by 1775!" Not so fast. The timing is suspect. Of the native-born colonists in 1775, many if not most of them would be at least second-generation. I don't have the numbers to determine how many were second- and third-generation, but it seems unlikely that a third-generation person would (independent of other conditions) be that much more disconnected from the homeland than the second-generation one. More intuitively, the big break in attitudes about the homeland would come between the initial immigrants and their first-generation native-born offspring. So why is the grandson of the immigrant all of a sudden taking up arms, and not the son? Why the 25 year waiting period? What's more, by 1775 there's no clear evidence of consistent, quickly identifiable cultural differences (e.g. a distinct accent) that would mark people as having been born on one side or the other of the Atlantic and thus drive a sense of colonial identity.
Another question would be what percentage of native-born people held high positions in the various colonial governments? I don't have access to such data and don't know if it exists, but a review of the birthplace of colonial governors shows no clear trends across the colonies. Pennsylvania had a number of native-born governors until 1763, when again it was run by British-born officials; Massachusetts was run by native sons starting in 1757 until administration was given back to an English-born military officer in 1774.
RICH ENOUGH TO QUIT
Another possible contributor to the break: colonial merchants and landowners had accumulated enough capital by the 1770s that they felt strong enough to challenge the Crown, but again that's speculation. Per capita income was higher, and taxation lower in the Americas on the eve of the Revolution. This greater wealth may have been a two-fold cause of the split: the colonies felt strong enough to revolt, and the Crown couldn't resist the chance to increase taxes on its wealthy colonies to cover its debt after decades of war. Of course, as we already know, the most obvious and direct cause for the Revolution was taxation, starting with the Stamp Tax just 2 years after the Treaty of Paris.
If this is the case, we should see something similar occurring in other British colonies as they become wealthier. We do suffer from a paucity of examples, but there has been one (and only one) other example of a revolt in an ethnic-majority-Anglo British colony that turned into a shooting war, the mystifyingly forgotten Canadian uprisings of 1837. I can't find data for per capita income at that time, or for that matter native:homeland ratio. In any event the revolt was not well-subscribed and was quickly put down, by a colonial government that also was interested in compromise in a way that they had not been 60 years earlier with the older colonies.
Moving out of the Anglophone world, it should also be pointed out that Mexico had been settled by Spain started in the early 1500s, and only revolted in 1810, undergoing this process almost a century and a half slower than the United States. (Arguably they only did so because of the external trigger of the Napoleonic Wars.) Given the much greater genetic and cultural admixture of natives with colonists in Mexico, it seems that national identity is not as important, though this could be confounded by an elite of greater European descent (still visible in Mexico today) that identifies more with Spain that the people and land around them.
I don't have enough data to make a revolution curve, but there are some qualitative statements I can make with moderate confidence. Chiefly, if you're going to govern people badly, and they're accumulating wealth and far away, you're not going to be governing them for long. And, "warm" cultural ties in the form of lots of people from the homeland living in the colonies seem not to be as important.
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