Spatially heterogeneous labeling efficacy. Simulations of a proliferating cell population, assuming two compartments with different labeling efficacy. Predicted overall label distribution m(x|t) during uplabeling (left), and probability densities p (x|i1) for particular division numbers i1 = 1 . . . 7 (right). For illustrative reasons, a low standard deviation within each compartment σ = 0.05 is assumed.