Forecasting US consumer behavior always has been a graveyard for economists’ reputations. The December plunge in spending took the market by surprise. But some facts are clear:

1) US retail sales are increasingly dependent on rising credit card balances;

2) Banks are more reluctant to extend more revolving credit lines, raising credit card interest rates to the highest level in history;

3) Household spending is extremely sensitive to changes in the price of necessities.

Banks are assessing an average rate of nearly 17% on credit cards. The last time the credit card rate was in this range, at 16.25% back in 1995, the prime lending rate to companies stood at 9%, vs. only 5.5% today. Banks are tightening financial conditions for consumers at a point where consumer spending is increasingly dependent on credit card loans.

Read more: US consumer still the world’s biggest macro risk