What does this actually mean? The world is a very big place, covered by lots of political, economic, and power systems.

The West - primarily, but not exclusively, the English-speaking parts - has seen a big change in the way politics is conducted, with less dignity and more verbal viciousness, but this hasn't really been matched by physical or "kinetic" politics. The sibling comment that there are fewer bombs going off is correct. Even Islamic fundamentalism has got less dangerous in the west - while the great middle eastern war started in 2001 rages on, expanding upwards to Nagoro-Karabakh.

If we want to talk stability, perhaps we should return to control systems theory. The feedback loops of the world have got shorter and faster. This moves the poles of the system around - and, without damping, makes it less stable.