["Review of Income and Wealth, Volume 72, Issue 3, August 2026. ", "\nABSTRACT\nThis study examines social mobility and its underlying drivers in Switzerland. We use a rich administrative dataset covering nearly 700,000 individuals across 23 birth cohorts. Rather than relying on traditional parent–child associations, we quantify the overall influence of familial factors, providing a wide‐ranging indicator of social mobility. Using two‐level linear mixed models, we find that family background accounts for 16.2% of the variation in income. Introducing an extensive set of economic and non‐economic parental characteristics reveals that their combined explanatory power is limited. Even when all considered parental factors such as income, education, working status, birth country, religion, civil status, language, or family size are included simultaneously, they account for less than 12% of the sibling correlation. These results highlight the comparatively modest role of observable parental characteristics in shaping income differences in Switzerland.\n"]