 It was triggered by a collapse in land and stock prices, which caused Japanese firms to have negative equity, meaning their assets were worth less than their liabilities.Despite zero interest rates and expansion of the money supply to encourage borrowing, Japanese corporations in aggregate opted to pay down their debts from their own business earnings rather than borrow to invest as firms typically do.Corporate investment, a key demand component of GDP, fell enormously (22% of GDP) between 1990 and its peak decline in 2003.