An estimated 22 percent of first-lien, residential home purchase loans originated in 2005 involved a “piggyback” loan, or a simultaneous second, up nearly 14 percent from 2004, according to the Federal Reserve Board’s analysis of the latest Home Mortgage Disclosure Act data. Piggyback financing has emerged in recent years as an alternative to traditional private mortgage insurance and an affordability strategy for cash-strapped homebuyers. In a typical piggyback transaction, a borrower takes...