RPDI, DSR, CCNR, and CCR denote real personal disposable income, the debt-service ratio, outstanding nonrevolving consumer credit, and outstanding revolving consumer credit, respectively. Estimation spans 1994 Q4 to 2008 Q3 inclusive allowing a maximum of ten basis functions and two variable interactions. The MARS sum of squared residuals based criterion function was adjusted by a penalty value of two with the dependent variable discretionary personal consumption expenditures. All series were transformed into their natural logarithms. Hansen stability tests refer to the Hansen  test (null: no structural change) and the associated probability values (in parentheses) for individual parameter stability, variance stability, and the hypothesis of joint stability. MARS is available at http://www.salford-systems.com/.