sentences:  Other proposed explanations have included the proliferation of human rights, increasing education and quality of life, changes in the way that people view conflicts (such as the presumption that wars of aggression are unjustified), the success of non-violent action, and demographic factors such as the reduction in birthrates.In the book "The Better Angels of Our Nature", Steven Pinker says that this is part of a trend that has continued since the beginning of recorded history, and other experts have made similar arguments.While there is general agreement among experts that we are in a Long Peace and that wars have declined since the 1950s, Pinker's broader thesis has been contested.