Investors were also anxious ahead of Federal Reserve Chair Janet Yellen’s speech in Jackson Hole, Wyoming Friday as many wait on hints over the central bank’s stand on its monetary policy.

Related: A Steady Economy, Potential Tax Reforms Help U.S. Stock ETFs Climb

Further weighing on the positive economic outlook, recent data revealed new U.S. single-family home sales unexpectedly dipped in July to a seven month low.

“With valuations elevated here, the market is going to be more vulnerable to short-term negative news and negative shocks,” Katie Nixon, chief investment officer at Northern Trust Wealth Management, told the Wall Street Journal. “But unless something really impacts the economy, it’s unlikely that the market impact will be long-lasting.”

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