Structural inequality shapes the daily rhythm of stationarity and mobility

Human mobility exhibits rhythmic patterns that shape economic activity, social interactions, and access to essential services. Yet, while prior studies focus on spatial movement, the temporal structure of people's stationarity-the act of dwelling-remains underexplored. Here, we introduce the Stationarity Sinusoidal Stability (STASIS) model to quantify the daily pulse of physical presence. Using three parameters-range, phase angle, and baseline-we show that majority-Black census block groups (CBGs) have smaller daily stationarity ranges, later activity peaks, and lower average home-presence baselines than majority-White and majority-Hispanic CBGs. The Rhythm Stability Index further indicates greater variability in activity timing among CBGs with higher proportions of Black residents, and this variability is associated with CBG-level economic precarity. Using COVID-19 as a stress test, our findings show that temporal stability in daily mobility rhythms differs across CBGs with different racial and Hispanic-origin compositions.