"Great powers and empires are, I would suggest, complex systems... They operate somewhere between order and disorder -- on 'the edge of chaos'... Such systems can appear to operate quite stably for some time; they seem to be in equilibrium but are, in fact, constantly adapting. But there comes a moment when complex systems 'go critical.' A very small trigger can set off a 'phase transition' from a benign equilibrium to a crisis... "
--Niall Ferguson

"What is most striking about this history is the speed of the Roman Empire's collapse. In just five decades, the population of Rome itself fell by three-quarters. Archaeological evidence from the late fifth century -- inferior housing, more primitive pottery, fewer coins, smaller cattle -- shows that the benign influence of Rome diminished rapidly in the rest of western Europe. What Ward-Perkins calls "the end of civilization" came within the span of a single generation."
---Niall Ferguson

"Other great empires have suffered comparably swift collapses. The Ming dynasty in China began in 1368, when the warlord Zhu Yuanzhang renamed himself Emperor Hongwu, the word hongwu meaning 'vast military power.' For most of the next three centuries, Ming China was the world's most sophisticated civilization by almost any measure. ...The transition from Confucian equipoise to anarchy took little more than a decade."
---Niall Ferguson

The most recent and familiar example of precipitous decline is, of course, the collapse of the Soviet Union. With the benefit of hindsight, historians have traced all kinds of rot within the Soviet system back to the Brezhnev era and beyond. ...governments in what was then called the Third World, from Vietnam to Nicaragua, had been tilting in the Soviets' favor for most of the previous 20 years. Yet less than five years after Gorbachev took power, the Soviet imperium in central and Eastern Europe had fallen apart, followed by the Soviet Union itself in 1991. If ever an empire fell off a cliff -- rather than gently declining -- it was the one founded by Lenin."
---Niall Ferguson

"If empires are complex systems that sooner or later succumb to sudden and catastrophic malfunctions, rather than cycling sedately from Arcadia to Apogee to Armageddon, what are the implications for the United States today? First, debating the stages of decline may be a waste of time -- it is a precipitous and unexpected fall that should most concern policymakers and citizens. Second, most imperial falls are associated with fiscal crises. All the above cases were marked by sharp imbalances between revenues and expenditures, as well as difficulties with financing public debt. Alarm bells should therefore be ringing very loudly, indeed, as the United States contemplates a deficit for 2009 of more than $1.4 trillion -- about 11.2 percent of GDP, the biggest deficit in 60 years -- and another for 2010 that will not be much smaller. Public debt, meanwhile, is set to more than double in the coming decade, from $5.8 trillion in 2008 to $14.3 trillion in 2019. Within the same timeframe, interest payments on that debt are forecast to leap from eight percent of federal revenues to 17 percent."
---Niall Ferguson [emphasis added]

"For now, the world still expects the United States to muddle through, eventually confronting its problems when, as Churchill famously said, all the alternatives have been exhausted. Through this lens, past alarms about the deficit seem overblown, and 2080 -- when the U.S. debt may reach staggering proportions -- seems a long way off, leaving plenty of time to plug the fiscal hole. But one day, a seemingly random piece of bad news -- perhaps a negative report by a rating agency -- will make the headlines during an otherwise quiet news cycle. Suddenly, it will be not just a few policy wonks who worry about the sustainability of U.S. fiscal policy but also the public at large, not to mention investors abroad. It is this shift that is crucial: a complex adaptive system is in big trouble when its component parts lose faith in its viability."
---Niall Ferguson [emphasis added]

"...empires behave like all complex adaptive systems. They function in apparent equilibrium for some unknowable period. And then, quite abruptly, they collapse. To return to the terminology of Thomas Cole, the painter of The Course of Empire, the shift from consummation to destruction and then to desolation is not cyclical. It is sudden."
---Niall Ferguson