The Globe and Mail reports in its Saturday edition that the S&P/TSX Composite Index and S&P 500 Index surged to record highs last week -- but investors should remember the big picture. The Globe's Ian McGugan writes that the market's returns over the past five years have been historically unusual. The S&P 500 has produced a total return of about 16 per cent a year since 2021 in Canadian-dollar terms. The Toronto Stock Exchange has also delivered outstanding results, churning out more than 15 per cent a year. Both indexes have doubled investors' money in five years. The folks at Capital Economics expect the S&P 500 to rise from its current level around 7,700 and hit 8,250 by the end of the year -- but they then expect the artificial-intelligence bubble to pop. The result will be a "major downturn" over the subsequent 12 months, they predict. Investors would do well to gauge their vulnerabilities. Mr. McGugan recommends building a cushion of cash or bonds to help carry you through any rough patch to come. Even if you're not near retirement, you might want to consider tilting your portfolio away from the AI frenzy. Some of us also see a case for bonds or guaranteed investment certificates.