Spectrem Group’s affluent investor index fell into neutral territory in July, abandoning the mildly bullish outlook it had registered since February 2004, the Chicago-based consulting firm said Wednesday.

The index, which measures the investment outlook of U.S. households with US$500,000 or more in investable assets, recorded by far its sharpest decline in the past six months, dropping eight points to a level of eight in July from 16 in June. This was the index’s second decline in three months.

Affluent investors expressed varying opinions when asked about the biggest threat to achieving their household financial goals. While 14% cited the economy as their primary concern in response to this open-ended question, job security, health and the presidential election were each chosen by 10% of respondents. The stock market followed at 9%.

“Affluent investors have grown substantially more cautious in their investment outlook, rejecting the mildly bullish sentiment they carried into the spring and looking broadly at those factors that could jeopardize their financial goals. The range of threats suggests the affluent may be feeling particularly ill at ease, as several of these concerns — specifically, job security and health — are almost completely out of their control. Interestingly, millionaires expressed less concern about these two issues than the broader affluent population,” said George Walper, Jr., president of Spectrem Group.

The Spectrem millionaire index, which measures affluent households with investable assets of $1 million or more, also declined eight points to 15 in July, but remained in mildly bullish territory, reflecting the somewhat greater level of optimism this group of investors has about its investment outlook.

The index is based on 250, 10-minute telephone interviews each month, giving the data a margin of error of plus or minus 6.2 percentage points. Interviews are conducted with the financial decision-makers in households with $500,000 or more in investable assets.