Confidence among affluent investors and millionaires declined considerably in June, according to a survey released Wednesday by Spectrem Group, a Chicago research company.

The Spectrem Millionaire Investor Index fell 11 points last month, to 6, it said, the biggest one-month drop since the index was begun in February 2004.

Affluent investors and millionaires both expressed sharply higher concern about inflation, citing it as the top threat to achieving their household financial goals.

Millionaires had persisted in a bullish outlook since late 2005, despite four consecutive declines through June in the broader Spectrem Affluent Investor Index.

The latter index, which measures the investment outlook in households with $500,000 or more of investable assets, lost 4 points in June to minus-1.

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