Americans confidence in the US economy dropped sharply in July to its lowest level in 2015, according to a new US Economic Confidence Index rating released by Gallup on Tuesday.

“Gallup’s Economic Confidence Index declined to an average of —12 in July from —8 in June. This is the lowest monthly average since last October, and is a noticeable departure from the +3 average in January,” the polling company said.

Gallup said that “unsettled economic” conditions, including tumult in Chinese markets and uncertainty in Europe over a Greek debt deal, as well as US stock market volatility are factors driving lower confidence in the US economy.

Starting in August 2014, Americans’ overall confidence in the US economy rose but remained in negative territory until January 2015, when the index hit positive territory for the first since the research company began its indexing in 2008.

In February, confidence in the US economy started to drop, which Gallup said was a result of high gas prices and reports of “disappointing” economic growth in the first quarter.

Gallup also found that there was a significant difference between upper-income Americans and those in the middle and lower income range. Economic confidence fell to —1 among upper-income Americans and —14 for middle-low income Americans in the month of July, which Gallup believes was due to a “fairly volatile” stock market in July.

US officials, including President Barack Obama and Federal Reserve Chair Janet Yellen, have said the US financial system and economy are largely insulated from the Greek financial crisis and Chinese markets.

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