US shale gas displaces coal (2007-2016)
Cheap shale gas from hydraulic fracturing flooded the US market. Coal's share of US electricity fell from about 50% to around 30% in under a decade as utilities switched fuels.
Coal plants closed or ran less; power-sector emissions dropped without any national mandate.
The US showed a dominant fuel can lose half its market fast when a cheaper rival scales up.
China's coal decline is driven by wind and solar rather than gas, but the pattern is the same: a cheaper competitor eats a fuel's share far faster than anyone predicted.
