So far as constraints on strategic choices are concerned, different political systems are associated with the relative emphasis on organized or unorganized conflicts respectively. Political 'exchanges' between organized labour and governments explain low levels of conflict in a number of countries. Moreover, in their absence, the strike is widely deployed as a form of political protest (especially where there are strong Communist Partytrade union ties). However, since the Second World War, a series of economic conditions such as movements in real wages, unemployment and inflation have been at the heart of strike activity in the west. These not only account for a number of variations amongst countries at a given point in time, but also the longer-term movements (notably the main cycles of conflict).