The head of global securitized products research at Citi Global Markets said that home equity held by American households is down from 60% to 39%. Mary Kane, speaking at an American Securitization Forum session about consumer trends and the state of the housing market, said residential mortgage comprised the largest proportion of debt held by families. The massive decline in home prices in the last few years is hitting those household investments hard, especially if families don't invest in other ways, such as with stocks and bonds. If families are not in the stock market, then recent rallies in those markets aren't helping them. In regards to falling home equity, Kane said it is important to keep perspective on the statistic. "When looking at this number, it's a very bifurcated number," Kane said. "One-third of homeowners don't have a mortgage, and another 20% are underwater." An estimated 14 million homeowners have negative equity, according to the ASF. Kane added that total U.S. debt is on a 10-year climb. The debt held by U.S. households in the fourth quarter of 2010 was 77% greater than in 4Q 2000, when including the effect of taxpayer exposure to the federal deficit. "I think it's extremely important that lenders and families take responsibility for taking on debt responsibly," Kane said, in an appeal to lenders to take a more proactive view of mortgages. "I don't feel that any regulatory proposals deal with underwriting or help families make responsible debt decisions," she added. Write to Jacob Gaffney. Follow him on Twitter @jacobgaffney.