1. Price. Cotton has cost 72% more per kg on average since 1992. At the 2011 peak — driven by China's government stockpile accumulation — cotton hit $5.06/kg, more than 5× polyester's price at that moment. Even at its cheapest (2001–2002: $0.82/kg), cotton was barely at parity with polyester, and that window lasted only 18 months before bouncing back. In globalized markets, cotton has never reliably been the cheap option.
2. Volatility. Cotton is 6.6× more volatile year-over-year than polyester. Cotton swings ±30% in a typical year; polyester swings ±5%. For fast fashion supply chains running on 3–6 month lead times and razor-thin margins, that volatility is operationally destructive. Manufacturers locked into cotton contracts got wiped out in 2011. Manufacturers running polyester had almost no price risk to manage.
3. Supply reliability. Polyester has no crop. No weather risk, no land competition, no harvest season. Cotton is exposed to drought (US), floods (Pakistan), government policy (China's stockpile and release cycle), export bans (India), and trade sanctions (Xinjiang). Every one of those events created price spikes and supply gaps that pushed buyers toward synthetics.
Cotton's price drivers are a compound of weather, geopolitics, agricultural policy, trade law, and currency. None of these have a polyester equivalent. Polyester's price drivers are narrow: oil cost and manufacturing overcapacity. That narrowness makes polyester predictable. Cotton's multi-factor exposure makes it structurally unreliable at scale — and that's the actual reason it lost market share.
