Changes in suicide inequalities in the context of an increase and a decrease in suicide mortality: The case of South Korea, 1995-2020

South Korea experienced a sharp increase until 2010 followed by a gradual decrease in suicide mortality. This study examined changes in socioeconomic inequalities in suicide over 25 years and how suicide inequalities changed in the context of both an increase and a decrease in suicide mortality. Data with five-year intervals were extracted from the Korean death registry and census data between 1995 and 2020. Using Poisson regression, four measures of suicide inequalities were calculated for the slope of inequality index (SII), relative index of inequality, rate ratios, and ratio differences. Educational inequalities in suicide were obvious across all sub-populations, measures, and periods. The widening of suicide inequalities, particularly with absolute measures, followed an increase in suicide mortality until 2010. In contrast, a decline of suicide inequalities concurred after 2010 during the period of a decline in suicide mortality. SII among the total population decreased by 35.4%, from 62.4 per 100,000 people (95% confidence interval [CI], 59.8-64.9) in 2010 to 40.3 (95% CI, 38.3-42.4) in 2020. The pattern of widening and narrowing in suicide inequalities observed in the whole population was only concordant with the older population. However, the younger and the middle-aged population showed a gradual increase or stalemate in the inequalities throughout the period. Overall, suicide inequalities narrowed in the recent decade. This decline was largely led by the older population, and was attributed to the provision of social protection. A decline of suicide inequalities can accompany a decline in suicide mortality, when the provision of social protection favored the less educated.