Confidence among wealthy investors rebounded in December last year, although pessimism still lingers, according to a report from US-based Spectrem Group.

The Spectrem Millionaire Investor Index rose 16 points in December to a reading of -23, marking the largest advance since the inception of the index in February 2004, Spectrem said in a statement.

In November, the index had slumped 15 points to a reading of -39, down from the previous record low of -24 in October.

Meanwhile, the Spectrem Affluent Investor Index, which measures the investment outlook for households with $500,000 to $1 million in investible assets, rose 8 points from its all-time low to a reading of -31 in December, but still remains in bearish territory. The index fell 9 points in November to a reading of -39.

Both groups of investors cited concern that the economy and market conditions were the greatest threats to achieving their financial goals.

“Millionaires and the affluent ended a dismal year on a relatively positive note, posting solid improvements in their investment outlook from record lows,” George Walper, president of Spectrem Group, said. “Nonetheless, both groups were far more pessimistic than a year ago.”

The indexes are put out on a monthly basis by the Chicago-based research firm.