The U.S. economy is on the cusp of entering its longest expansion in the postWorld War II era, but longevity often raises questions about sustainability. Moreover, the scarring experience of the financial crisis, which was triggered by an unsustainable build-up in mortgage debt, is still fresh in the minds of many market participants, and the rising level of U.S. debt in recent years is a source of concern among some observers. As shown in the top chart, the combined debt of the household, business, government and financial sectors in the United States totaled $4.3 trillion in 1980. Total American debt grew non-stop ... (full story)