The Diverging Action-Space: Evolving Rhythms and Changing Habits in Daily Mobility

How much has daily mobility changed in an era of digitization, remote work, and a global pandemic? Using 17 years of Danish travel data (>140,000 individuals), we analyze daily action-spaces—the distance from home over time—across five age cohorts. We identify a two-regime structure. The conditional action-space envelope describing where people go when they travel shows systematic spatial expansion: younger cohorts (10–30 years) exhibit the strongest increases (+8–14%), but working-age adults and seniors also travel farther when away from home. Temporal rhythms within this envelope remain remarkably stable. In contrast, the unconditional propensity to leave home has declined sharply for those under 55: younger cohorts spend substantially more time at home despite their spatial expansion, while adults aged 31–55 show similar but weaker temporal contraction. Pre-retirement and older adults (55 years and older) exhibit near-zero temporal drift. This age-stratified divergence—widespread spatial expansion coupled with life-stage-dependent temporal contraction—suggests the emergence of cohort-specific behavior and raises the possibility of a "stay-home generation," challenging standard assumptions in mobility forecasting and urban planning.