The Outsourced Drug Discovery segmentation by type isolates four functionally distinct service clusters that collectively shape market value. Medicinal-chemistry services, commanding ~30 % of 2023 external spend, generate revenue through iterative hit-to-lead optimisation contracts priced per compound; demand elasticity is tightly linked to sponsor pipeline refill cycles. ADME-Tox represents 24 % of outsourced wallets and is growing fastest because regulators now expect comprehensive off-target liability packages before IND filing; providers price on a per-assay grid, so throughput scale directly expands segment dollars. Biology services (22 %) cover target validation, cell-line engineering and phenotypic screening; although average unit prices are eroding 4 % annually, volume offsets from novel modality programs (e.g., bifunctional degraders) keep absolute segment value flat in real terms. Pharmacology & animal-model studies, holding 24 % share, remains indispensable for human dose projection; increased pressure to replace in-vivo work with imaging surrogates is trimming historical CAGR to 2 %, but higher-tech models (humanised mice, PDX) partly restore pricing power.