Parent and McDonald survey power transitions since 1870 (when data on gross domestic product first started being reliably collected) to explore the behavior of both the top states in the order and the lesser but still powerful states. They examine 16 cases of relative decline, some by hegemonic powers and some by mid-level states.

What they find is that most states respond sensibly to relative decline, undertaking prompt, proportionate retrenchment, because they seek strategic solvency—they don’t want to go bankrupt (and thus lose their independence). That is, the sensible policy choices that helped make them powerful also help them cope with straitened circumstances and decide to reduce their military and avoid armed conflicts. For most states, the choice of retrenchment helps them regain stature; those that fail to retrench never do.

The authors also find that states experiencing decline are not generally seen as inviting targets for aggression by others. So rising states are not generally tempted to attack a weakening rival. Parent and McDonald’s research suggests this is because the states experiencing decline steer clear of conflicts—war being the unsentimental arbiter of state power, declining states would rather not risk demonstrating their diminution. Their research also suggests that these states tend to prevail in the conflicts they do choose to initiate. Parent and McDonald conclude, “This suggests that declining powers are flexible and formidable.”