In September 2015, leaders of the world called for a ‘new chapter’ in global development to be achieved by 2030 through 17 Sustainable Development Goals. Today, we are close to the halfway point and many challenges remain so no one is ‘left behind’. One key condition for achieving sustainable development and all SDGs consists in promoting just, peaceful, and inclusive societies (SDG 16). In this era of seemingly insurmountable problems, from poverty and inequality to climate change, it is important to highlight that only political systems and institutions which meet the standards of SDG 16 are able to deliver all SDGs sustainably over time. SDG 16 is largely focused on a number of cross-cutting values upon which delivery of all of the SDGs depend. These include democracy - understood as popular control over public decision making and equality in the exercise of that control- respect for human rights and the rule of law, and effective, transparent and accountable public institutions. Without these influences in decision-making, it is unlikely that the needs of the people —from quality education (SDG 4) to climate action (SDG 13)—will be listened to and addressed by governments. The SDG16 Data Initiative makes the argument for peace, justice, and strong institutions as a threshold condition for development, illustrating the linkages between goal 16 and other goals. Despite its importance, the evidence so far suggests that we are a long way from achieving the targets under SDG 16. The Initiative will therefore provide a half-way diagnosis and look ahead to the challenges for the next seven years, providing key policy recommendations.