Then, last year, China watchers added another 40% of debt/GDP to the total when, as S&P calculated, China's local governments had accumulated 40 trillion yuan ($6 trillion) - or even more - in off-balance sheet, or Local government financing vehicles (LGFV) debt, an amount Bloomberg has dubbed China's "hidden debt bomb", suggesting the already record surge in defaults in 2018 is set to accelerate further.

"The potential amount of debt is an iceberg with titanic credit risks," S&P credit analysts wrote in October 2018, with much of the build-up related to local government financing vehicles, which don't necessarily have the full financial backing of local governments themselves.