(Bloomberg) -- Stock markets are risking an unsustainable "sugar high" as investors price in a pro-growth agenda from Donald Trump's administration that may not be supported by an improvement in the economy, according to the world's largest mutual-fund company.

It would take "very little to end up with a market correction because of higher valuations," Tim Buckley, chief investment officer of Vanguard, said in an interview at his company's London office this week. "You are teetering from a height and it's easy to lose your balance. It takes a little bit from the outside, and volatility returns to the market."

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