Cross-sectional income studies often tend to give the impression that people's economic status is relatively stable and static. However, longitudinal data have shown that changes in economic well-being are surprisingly frequent over the life course. This paper examines economic mobility in Sweden in comparison with earlier American findings. A primary focus of attention is to explore whether the great impact of “family composition changes,” as a major cause of economic change in the United States, is also present in Sweden. The findings show the importance of changes in family composition in both countries, but this impact varies strongly both between different subgroups of each population and when comparing the subgroups cross-nationally. Whereas family composition changes are tied to changes in economic well-being for women in both countries, this connection does not hold for American men and Swedish children.