Millionaires' confidence in the economy and present market conditions dropped to a 16-month low.

Spectrem's Millionaire Investor Confidence Index in June dropped to six points from 15 in May. The market research firm's Affluent Investor Confidence Index dropped just two points to six.

Though June's results mark the first time since February 2010 that millionaire and affluent investors have reported the same level of confidence (six points on Spectrem's indexes), millionaires were marginally more focused on the market at large. Twenty percent of millionaires cited market conditions as the "most serious threat to achieving household goals," compared to 17% of affluent investors.

Concerns about China and turmoil in Greece, along with growing speculation about the Federal Reserve were leading factors in the decline in investor confidence, according to the survey.

"In light of everything happening in Greece, investors are going to be concerned about whether the initial shock in the markets is going to keep happening, the more the situation in the EU goes unresolved," says Randy Wostratzky, director of wealth markets and retirement research for Spectrem Group.

Advisors will want to address some of that concern, Wostratzky says. "They must also be able to communicate to clients the possible interest rate implications if the Fed were to begin raising rates in September like some are speculating."

Though June's results mark the first time since February 2010 that millionaire and affluent investors have reported the same level of confidence (six points on Spectrem's indexes), millionaires were marginally more focused on the market at large. Twenty percent of millionaires cited market conditions as the "most serious threat to achieving household goals," compared to 17% of affluent investors.

But millionaires were less concerned than their non-millionaire counterparts about the economy hindering their ability to accomplish their financial goals (12% vs. 15%).

The two groups were almost on the same page in their views of how the political landscape is affecting their goals. Thirteen percent of millionaires and 14% of affluent investors cited the political climate -- marked by the controversial Supreme Court rulings last week, the recent shooting at a historic black church in South Carolina and the entry of 16 hopefuls to the 2016 presidential race -- as a serious threat.

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