Historical demographers, anthropologists, and economic historians have commonly used conscript height at around age 20 as a proxy for well-being, assuming it reflects the nutrition and health of a fully-developed man. However, this approach may prove problematic if men are not yet fully grown at conscription. This study addresses this concern by constructing an individual-level panel of 2,916 men born in 1887 in Corrèze, France, using two conscription records. The analysis reveals that while most men experienced only minimal height increase (0.3–0.4 cm) in the year after turning 20, indicating near-complete physical maturation, a subset of the panel differed markedly. The 20% of men identified as the most physically vulnerable continued to grow substantially, gaining an additional 1.5 cm before reaching adult height around age 27. These findings suggest that relying on height at age 20, rather than adult stature, can lead to underestimating available resources and to overstating how unequally they are distributed.