This study addresses these two shortcomings, by using an alternative poverty measure recently developed by the U.S. Census Bureau and U.S. Bureau of Labor Statistics, the Supplemental Poverty Measure (SPM), in place of the OPM to determine who qualifies as poor, and by analyzing poverty from a longitudinal rather than cross-sectional perspective, examining chronic or long-term poverty and transient or short-term poverty as distinct phenomena. Prior research has examined poverty in the U.S. using alternative poverty measures including the SPM, but only from a cross-sectional perspective. Other research has examined U.S. poverty from a longitudinal perspective, but using the OPM or a closely derived poverty measure. This study thus fills a gap in the existing research on poverty in the United States, by measuring poverty longitudinally using the better-grounded Supplemental Poverty Measure.