Responded to the main question correctly - global debt grew by $ 57 trillion 7 years after the global credit bubble burst.
Covered sub-question on what are the challenges and why: increase in government debt by $25 and challenges:
a) Ratio of debt to GDP up 17%, Recession and weak recovery,
b) Financial bailouts and stimulus programs,
c) Is this level of debt sustainable?
Sub-question on what are increases/challenges and why: increase in household debt and challenges:
a) Higher debt-to-income ratios in countries like Canada, Australia, Sweden, etc. have exceeded peak levels.
b) How to manage household debts safely
Sub-question on what are increases/challenges and why: China's debt increased to $28 trillion and challenges:
a) Linked to overheated real-estate market,
b) Unregulated shadow banking.
c) Debt to many local governments unsustainable?