(AP) — American consumers stepped up their borrowing by $18.4 billion in December, a solid performance that followed a massive gain the previous month.

The increase reflects gains of $5.1 billion in the category that covers credit cards and $13.3 billion in the category for auto and student loans, the Federal Reserve reported Wednesday.

The overall increase followed a $31 billion surge in November as consumers took on extra credit to finance holiday shopping.

Consumer borrowing is closely followed for indications about how confident households are in taking on more debt to finance spending, which accounts for 70 percent of economic activity. In the fourth quarter, the overall economy grew at a solid 2.6 percent rate. In recent months, Americans have been increasingly confident and willing to take on more debt.

The question is whether the sharp declines in the stock market last Friday and Monday could shake that confidence. Moreover, the Federal Reserve raised its benchmark rate three times in 2017 and indicated in December that it planned to boost rates another three times in 2018 to keep the economy from overheating now that unemployment has dropped to a 17-year low of 4.1 percent.

The five rate increases the Fed has approved over the past two years have left the central bank’s key rate at a still-low range of 1.25 percent to 1.5 percent.

The overall increase in credit in December pushed the total to a record of $3.84 trillion. The monthly gain was a 5.8 percent increase in percentage terms, which followed the 9.8 percent surge in November. That had been the biggest percentage increase since a similar percentage gain in July 2011.

During the first few years of recovery from the Great Recession, Americans paid down or defaulted on debts that had been run up during the housing bubble that preceded the downturn. But in the past two years, Americans have increasingly been willing to borrow more, particularly for student loans and auto loans.

The Fed’s monthly consumer borrowing report does not cover home mortgages or any other loans secured by real estate such as home equity loans.