In broad brush, Christmas (along with all other consumer spending) has been funded by financialization, i.e. debt and leverage, not by increased earnings.

The primary financial trick that's propped up the "recovery" for seven years is piling more debt on stagnating incomes. How does this magic work? Lower interest rates.

In a healthy economy, households earn more money (after adjusting for inflation, a.k.a. loss of purchasing power), and the increased earnings enable households to save, spend and borrow more.

In an unhealthy, doomed-to-implode economy, earnings are declining, and central banks enable more borrowing by lowering interest rates to zero and loosening lending standards so anyone who can fog a mirror can buy a new pickup truck with a subprime auto loan.