As homeowners see the value of their homes decline, they become more likely to delay purchases of the big items - like automobiles, electronics and home appliances - that are ballasts of the American economy. When those purchases decline, large manufacturing firms, suddenly short on funds, could begin laying off employees.

As the United States has become an older nation, reverse mortgages have grown into a $20-billion-a-year industry, with elderly homeowners taking out more than 132,000 such loans in 2007, an increase of more than 270 percent from two years earlier.

Even if consumer confidence hit rock bottom, that most likely would not be enough, by itself, to cause a depression.

Charles Duhigg Quotes