Liberal republics offer many advantages over other systems, including and beyond freedom.
They offer more domestic security. They tend to see less internal violence. This relationship can be seen in the figure above. It includes data on 151 countries for the years 2006 through 2018, compiled by the Center for Systemic Peace. Liberal, republics are far less likely to kill their citizens than autocratic governments. Liberal, republican democracies are also less likely to go to war with each other, though they do go to war with illiberal republics and non-democracies. The more stable, peaceful environments found in democracies promotes innovative investments by reducing the risk of violence.
 See Rummel (2017). Power kills: Democracy as a method of nonviolence.
 There are many theories why democracies have not gone to war with one another. For one example, see Owen, J. (1994). How liberalism produces democratic peace, International Security, 19(2), pp. 87-125.
Excerpted from Democracy is Precious.