US stocks have risen to all-time highs this year. Should you ‘sell in May and go away’?

The hypothesis is that equities tend to underperform in the six months through October, so investors should sell stocks at the start of May, invest in cash and then re-enter the market in late autumn, the strategists said.

“In the U.S., a stay invested strategy has tended to outperform, particularly in recent years,” the strategists said.

The technology sector now accounts for 27% of the S&P 500, or much higher than the 8% weighting for the MSCI Europe index, according to UBS.

Over the past 15 years, returns in Europe have been negative in June 80% of the time, according to the report.

The S&P 500 rose to a record 4,211.47 finish on April 29, for example, and was up 11.3% this year as of Friday’s close.

“We are now entering a time of year when stocks have historically found it more challenging to advance,” according to the UBS report.

Ryan Detrick, chief market strategist for LPL Financial, said in a blog Friday that the six months from May through October have been “some of the weakest months of the year for stocks” in the past 10 years.

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