AbstractBackgroundSocioeconomic differences in mortality among the working-age population have increased in several high-income countries. The aim of this study was to assess whether changes in the living arrangement composition of income groups have contributed to changing income differences in life expectancy during the past 30 years.MethodsWe used Finnish register data covering the total population to calculate partial life expectancies between ages 35 and 64 by income quartile in 1988–2017. The contribution of living arrangements to these differences was assessed by direct standardization. Decomposition methods were used to determine the extent of life expectancy differences due to external (accidental, violent and alcohol-related) causes of death.ResultsThe life expectancy gap between the highest and lowest income quartile increased until 2003–07, but decreased thereafter. The contribution of living arrangements to these differences remained mostly stable: 36–39% among men and 15–23% among women. Those living without children consistently showed the greatest life expectancy differences by income. External causes of death significantly contributed to income differences in life expectancy.ConclusionsThe living arrangement composition of income groups explained part of the differences in life expectancy, but not their changes. Our results on the contribution of external causes of death imply that both the persistent income gradient in mortality as well as the mortality disparities by living arrangements are at least partially related to similar selection or causal mechanisms.