【徐瑾】全球数据显示中产阶级在数量、收入占比与财富份额上持续下滑：按日均收入10美元的宽松口径，中产曾被视为逾20亿，但以更严格的50美元门槛，2015年数据显示其中87%集中在欧美，而美国对应比例已由2001年的58%降至2011年的56%。1970年以来美国中产收入增速长期落后上层；2000–2014年间中产在九成大城市萎缩，其中位收入由77,898美元降至72,919美元（跌幅6%）。全球层面，联合国2025年数据称28亿人日均仅2.15–6.85美元，约65%人口所在国家收入差距扩大，而世界各地区1980–2016年前10%收入份额普遍上升：欧洲37%，中国41%，北美47%，中东达61%。

财富分布的极端化进一步加剧中产压力。UBS称2024年全球近6,000万百万富豪掌握226万亿美元、约占全球个人财富一半，对比2017年最富1%已占45.9%。乐施会报告显示2024年最富人群财富从13万亿增至15万亿，为记录第二高增幅，同时44%人口生活在6.85美元贫困线下。美国80年代后不平等急剧反转，前10%收入份额自不足35%升至45–50%，金融危机后贫弱群体租金负担更恶化：贫困租房家庭需将逾50%收入用于住房，至少四分之一需支付70%以上；密尔沃基每年约16,000人被驱逐，每八名租户中一人经历强制迁出。

跨国趋势显示阶层上升通道收窄，即所谓“S型社会”结构：中国、美国、印度等均出现中等收入群体停滞或倒退。印度1980–2014年前1%吞下三分之一收入增长，富裕阶层收入较80年代上涨十倍，而中等收入群体未能实现倍增，八成民众认为不平等与腐败同样严重。全球层面“富者更富、穷者更穷”伴随行业周期加速、技术替代与组织稳定性下降，使中产面临职业中断、收入波动与流动性下降，构成全球中产下沉的结构性基础。

Global data show sustained declines in the size, income share, and wealth share of the middle class. Under the loose threshold of USD 10 per day, the middle class once appeared to exceed 2 billion, but under the stricter USD 50 cutoff, 2015 data show 87% located in Europe and North America, with the U.S. share falling from 58% in 2001 to 56% in 2011. Since 1970, U.S. middle-class income growth has lagged upper-income groups; between 2000 and 2014 the middle class shrank in 90% of major cities, and median income fell from USD 77,898 to USD 72,919 (a 6% drop). Globally, a 2025 UN report finds 2.8 billion people living on USD 2.15–6.85 per day, about 65% of populations face widening inequality, and from 1980–2016 top-10% income shares rose widely: Europe 37%, China 41%, North America 47%, Middle East 61%.

Wealth concentration has intensified pressures. UBS reports nearly 60 million millionaires in 2024 controlling USD 226 trillion—about half of global personal wealth; in 2017 the richest 1% already held 45.9%. Oxfam reports the wealth of the richest grew from USD 13 trillion to USD 15 trillion in 2024, while 44% live under the USD 6.85 poverty line. U.S. inequality reversed sharply after the 1980s as the top-10% share rose from under 35% to 45–50%. Housing burdens worsened for the poor: over 50% of income spent on rent for most low-income renting families, at least a quarter spending above 70%; Milwaukee sees ~16,000 evictions yearly, with one in eight renters experiencing forced displacement.

Cross-country patterns show narrowing mobility channels—an “S-shaped society.” China, the U.S., and India all exhibit stagnation or decline of middle-income groups. In India, 1980–2014 top-1% captured one-third of income growth, grew tenfold wealthier, while middle incomes failed to double; 80% view inequality as severe. Accelerating industry cycles, technological substitution, and declining organizational stability heighten job disruption, income volatility, and reduced upward mobility, forming the structural basis of global middle-class erosion.