Attention has a seemingly inevitable tendency to turn inward toward our thoughts. Mind-wandering refers to moments when this inward focus diverts attention away from the current task-at-hand. Mind-wandering is thought to be ubiquitous, having been estimated to occur between 30% and 50% of our waking moments. Yet, it is unclear whether this frequency is similar within-task performance contexts and unknown whether mind-wandering systematically increases with time-on-task for a broad range of tasks. We conducted a systematic literature search and individual participant data meta-analysis of rates of occurrence of mind-wandering during task performance. Our search located 68 research reports providing almost a half-million total responses to experience sampling mind-wandering probes from more than 10,000 unique individuals. Latent growth curve models estimated the initial occurrence of mind-wandering and linear change in mind-wandering over sequential probes for each study sample, and effects were summarized using multivariate meta-analysis. Our results confirm that mind-wandering increases in frequency over time during task performance, implicating mind-wandering in characteristic within-task psychological changes, such as increasing boredom and patterns of worsening behavioral performance with time-on-task. The systematic search and meta-analysis provide the most comprehensive assessment of normative rates of mind-wandering during task performance reported to date. (PsycInfo Database Record (c) 2025 APA, all rights reserved).