Final answer:
The one-child policy in China led to a projected shortage of working-age people, causing increased costs for the elderly and severe social impacts like gender imbalances and potential labor shortages.
Step-by-step explanation:
An unintended consequence of China's antinatalist one-child policy is a projected shortage of working-age people to care for the rising elderly population, resulting in an increase in the cost of living for older people. The one-child policy, implemented to control rapid population growth and alleviate economic and environmental concerns, led to a demographic imbalance with skewed sex ratios due to a cultural preference for male heirs, resulting in increased incidences of sex-selective abortions and female infanticide. Despite the reduction in birth rates and population growth, the policy has had significant social impacts, which include an aging population, gender imbalances, and potential labor shortages.