Borrowing Up for Third Straight Month : Economy: String of gains in installment credit is longest in two years. Figure, along with other indicators, shows a jump in consumer confidence.

Americans increased their borrowing in November for the third consecutive month, the longest string of advances in two years, the government said Friday.

Outstanding consumer installment credit rose at a seasonally adjusted annual rate of 2% to $723.9 billion, the Federal Reserve said. It rose 0.9% in October and 2.4% in September.

The last time outstanding credit increased three months in a row was September-November, 1990. Before the latest gains, outstanding credit had shrunk for seven consecutive months.

The November report fits with other economic indicators, including surveys showing a jump in consumer confidence after the presidential election and chain store reports showing the best Christmas sales in four years.

But economists warn that the spending won’t continue unless businesses pick up the pace of their hiring.

“Ultimately, for the upturn in consumer spending to be sustained, job growth has to be better because job growth affects income growth,” said economist Allen Sinai of the Boston Co.

Sinai said the most recent job gain reported by the Labor Department, 64,000 in December, “might not sustain the optimism of the household sector that we’ve seen develop since the election.”

Consumer spending, which represents two-thirds of all economic activity, is crucial to the recovery. During and after the recession, outstanding loans shrank as cautious consumers reduced the debt they had incurred during the 1980s.

In November, outstanding revolving loans edged up at a seasonally adjusted annual rate of 0.5% to $250.6 billion, the fourth consecutive increase.

Automobile loans jumped up at a 3.3% annual rate to $257.8 billion, following a 1.3% decline in October.

Other consumer loans advanced at a 2.3% annual rate to $215.5 billion. This category includes loans for mobile homes, education, boats, trailers and vacations.

The various changes left total consumer debt not secured by real estate at the highest total since March.