文章以「人口算术」说明：人口变动取决于出生减死亡，再加上移入减移出。美国人口增速已降至疫情以来低点，净移民从高峰回落，出生多于死亡的差额也在缩小，未来可能在 2030 年左右消失，届时人口成长将更依赖移民。部分研究甚至推算 2025 年已接近或出现净负移民，若 2026 年净移民进一步转负，总人口就可能转为下降。
特朗普政府主张减少移民能提高本地工人机会与薪资、降低住房与医疗等成本，并宣称正终结「大规模移民时代」。但多位经济学者警告，较低移民与潜在人口下降对经济的伤害更可能在中长期显现，影响 GDP 增长、劳动供给与财政可持续性（如社保与债务）。未来影响究竟是短暂波动还是长期新常态，取决于政策走向与政治选择。
The US has long relied on immigration as a durable advantage that expands its population and economic weight, but Trump’s second-term crackdown is accelerating the moment when net migration no longer offsets falling births and rising deaths in an aging society. That shift raises the possibility that 2026 could bring the first meaningful population decline in US history, far earlier than earlier long-range forecasts suggested.
The mechanics are straightforward—births minus deaths plus net migration—but the data are messy and often lag policy changes. Recent official estimates show sharply slower growth driven largely by a collapse in net migration, while other analyses argue the country may already be near or below zero net inflows. If net migration turns sufficiently negative, it could outweigh the still-positive (but shrinking) natural increase and push the total population into decline.
The administration argues fewer immigrants will reduce competition for jobs and housing and improve outcomes for native-born workers, while critics contend the broader macro effects are more corrosive over time: weaker GDP growth, a tighter labor supply, and added fiscal strain as the working-age base supports an older population. Whether this becomes a temporary blip or a new normal depends on how durable the policy regime proves and whether future politics reverse or entrench the current approach.