Does Social Capital Deserve Its Own Sustainable Development Goal? Evidence for a Trust Indicator under SDG 16

Across 155 countries, social capital is linked to Sustainable Development Goal performance almost entirely through governance quality. Using a balanced panel for 2007–2023 that combines Legatum and World Values Survey measures with the SDG Index and the Worldwide Governance Indicators, the paper tests whether social capital warrants a goal of its own, a proposal that has so far rested on conceptual argument. One standard deviation of social capital is associated with an SDG Index 1.78 points higher through governance, against a direct effect of 0.02. The same channel carries its association with income, innovation and lower conflict incidence, while its link with poverty disappears once income is controlled. Within countries the SDG Index association vanishes after common factors are removed, and this null is precise enough to exclude effects one third the size of the between-country gap. The results support adding a generalized-trust indicator to SDG 16 and give no support to a separate goal.