Table 1.

Examples of coupled subsystems in which each subsystem undergoes sudden changes in the form of saddle-node bifurcations, in models cited in the column ‘regime shift'. The column ‘scalar quantity' describes the state of the subsystem, and it corresponds to x(t), y(t) or z(t) in the model in §2. Citations in the fourth column include empirical studies and mathematical models.

discipline	regime shift	scalar quantity	examples of couplings among subsystems
ecology	extinction due to over-harvesting [15,16]	population	diffusion among patches of an ecosystem [2,4]
economics	boom and bust in the Kaldor model of business cycles [17]	output (gross domestic product)	investment between sectors [18], trade [13] and capital flows [19] between countries can synchronize business cycles
economics	currency crisis (devaluation or, for a peg, loss of reserves) [20]	currency value	changes in macroeconomic fundamentals, sentiment, perceived riskiness, risk aversion [20] and trade [21]
economics	poverty trap [22,23]	well-being (capital, capabilities)	fractal poverty traps [9]
finance	asset price declines [24,25]	asset price	asset-to-asset contagion (a bank with a declining asset sells other assets) [26]
finance	probability of bank failure [27]	probability of bank failure	worry about institutions' creditworthiness spreads contagiously [28]
technology adoption	sudden change to new platform [13,29]	difference between supply and demand of the new platform	movement of people among distinct markets [14]
political	uprisings, revolts [30,31]	number of protestors	communication spreads inspiration, successful strategies across borders [11,12,32,33]; raising importance of identity [31] that span borders [34]