Large language models (LLMs) are increasingly used in culturally sensitive settings, where alignment requires representing diverse preferences within populations. Yet existing methods model populations at coarse demographic or community levels and overlook within-group variation. We introduce DEMOGRAPHIC PLURALISM, an inference-time framework that estimates population-level opinion distributions without opinion-distribution training data or task-specific fine-tuning by generating multiple perspectives within census-grounded demographic groups. Across four backbones on GlobalOpinionQA and VITAL, it reduces Jensen–Shannon distance by 8.4%–26.4% over Modular Pluralism. Among weighted, equal-weighted, and inverse-weighted aggregation, equal weighting performs best overall; group-level error also increases with census weight, helping explain weighted aggregation’s weaker performance.