The canonical answer is of course the 1997 Asian financial crisis. The crisis greatly strained governmental and municipal budget available for pretty much every

The canonical answer is of course the 1997 Asian financial crisis. The crisis greatly strained governmental and municipal budget available for pretty much every public infrastructure and the 1998 Act on Private Investment in Social Overhead Capital Facilities (사회간접자본시설에 대한 민간 투자법) was introduced to fill this gap. The problematic minimum revenue guarantee stems from this law, originally intended to encourage private investment, and while the law was subsequently fixed in 2006 many infra projects built around 2000 including the Seoul Subway Line 9 still suffer from its consequences.