Human-Centered Effective Demand Constraints, Product Replacement Cycles, and Industrial Growth Boundaries

Production capacity does not automatically translate into sustainable industrial growth. This paper develops an analytical framework of "human-centered effective demand constraints," decomposing realizable industrial demand into a set of primary constraint filters. With Demand Boundary (D), Budget Capacity (B/p), and Replacement/Purchase Opportunity (R) as core constraints, the framework incorporates Enabling Environment (E), Institutional and Cultural Access (I), and Anticipation/Policy Signals (A) as extensible constraints depending on industry and market characteristics. A two-good optimization model shows that optimal durable purchases exhibit a min structure and a kink: once a use or replacement ceiling binds, further relaxation of the budget constraint no longer raises purchases proportionally. The paper further replaces the mechanical S/T rule with a general replacement equation in which current replacement demand is a convolution of historical sales and age-specific retirement hazards; S/E(T) is retained only as a steady-state approximation for mature markets. Using China's 2025 official statistics, the paper shows substantial heterogeneity across durable categories. Refrigerators and washing machines are close to one unit per household, while air conditioners and household cars still exhibit stock expansion. New-energy vehicles account for only 12.01% of the automobile stock but 49.38% of new registrations, demonstrating that aggregate-market maturation and rapid subcategory diffusion can coexist within the same industry. The paper further incorporates exports into the demand envelope, distinguishing between domestic effective demand, sustainable exports, and capacity planning. The framework provides an operational way to distinguish growth driven by diffusion, replacement, upgrading, environmental improvement, access expansion, and market expansion, offering implications for capacity planning, trade-in policies, and international market entry assessment.