... Siegel struck out on his own, investing in distressed consumer debt — basically buying up the right to collect unpaid credit-card bills. When debtors stop paying those bills, the banks regard the balances as assets for 180 days. After that, they are of questionable worth. So banks “charge off” the accounts, taking a loss, and other creditors act similarly. These huge, routine sell-offs have created a vast market for unpaid debts — not just credit-card debts but also auto loans, medical loans, gym fees, payday loans, overdue cellphone tabs, old utility bills, delinquent book-club accounts. The scale is breathtaking. From 2006 to 2009, for example, the nation’s top nine debt buyers purchased almost 90 million consumer accounts with more than $140 billion in “face value.” And they bought at a steep discount. On average, they paid just 4.5 cents on the dollar. These debt buyers collect what they can and then sell the remaining accounts to other buyers, and so on. Those who trade in such debt call it “paper.” That was Aaron Siegel’s business.