If there is one common theme to the vast range of crisis we consider in this book, it is that excessive debt accumulation, whether it be the government, banks, corporation, or consumers, often poses greater systemic risks than it seems during a boom.  Infusions of cash can make a government look like it is providing greater growth to its economy than it really is. Private sector borrowing binges can inflate housing and stock prices far beyond their long-run sustainable levels, and make banks seem more stable and profitable than they really are. Such large-scale debt buildups pose risks because they make an economy vulnerable to crisis of confidence, particularly when debt is short term and needs to be constantly refinanced.  Debt-fueled booms all too often provide false affirmation of a government’s policies, a financial institution’s ability to make outsized profits, or a country’s standard of living.  Most of the these booms end badly.  Of course, debt instruments are crucial to all economies, ancient and modern, but balancing the risk and opportunities of debt is always a challenge, a challenge policy makers, investors, and ordinary citizens must never forget.

From This Time is Different- Eight Centuries of Financial Folly by Carmen M. Reinhart & Kenneth S. Rogoff