Population Dynamics Foundation Models (PDFM) produce socio-economic latent embeddings — 330- or 512-dimensional in Planetary Prediction Engine papers — that complement explicit statistical covariates. Google Research's PPE fuses PDFM vectors with AlphaEarth satellite embeddings and Data Commons / Earth Engine covariates. Across PPE ablations, structured covariates and PDFM embeddings are treated as complementary rather than redundant; the DRC Ebola nowcast fuses epidemiological signals with PDFM and PPE-selected geospatial covariates.