Dynamic Simulation of Long-Term Demand for Different House Types in Bangkok Utilizing the System Dynamics Modeling Approach

Understanding joint influences of household composition and financial capacities on housing demand is vital for informing long-term urban development and policy planning in Bangkok. This study presents a system dynamics (SD) model to simulate scenario-dependent demand across condominiums, townhouses, and detached houses over a 15-year planning horizon. The model integrates housing-stock accumulation, household-size and income distributions, mortgage debt-service calculations, affordability-based allocation mechanisms, and price-dependent take-up behaviors. Model performance was validated through historical data, dimensional verification, and sensitivity analyses, encompassing housing-price growth, household-income growth, debt repayment-to-income thresholds, and loan payment period. Under baseline conditions, condominium demand consistently exceeds that of alternative housing typologies, while detached-housing units exhibit steady incremental growth. Low-income townhouse units become positive at simulation year 13 upon crossing the designated affordability thresholds. Sensitivity analyses reveal that house price is more sensitive than household income. Expanding permissible debt repayment-to-income ratios from 28% to 36% and extending loan tenures from 30 to 40 years enhance modeled purchasing capacities, though these responses represent conditional outcomes tied to underlying credit assumptions rather than verified credit approval rates or guaranteed policy outcomes. The results emphasize the necessity of jointly evaluating housing valuation, household earnings, and financing structures when designing housing support mechanisms. Given the structural constraints of prescribed allocation rules and validation data, the resulting trajectories are better interpreted as exploratory scenario projections rather than definitive, standalone forecasts. Consequently, the model offers an analytical framework to support policy dialogues and development planning alongside empirical market indicators.