The Globe and Mail reports in its Saturday edition that Scotiabank strategist Simon Fitzgerald-Carrier is warning clients about market concentration in U.S. markets. The Globe's Scott Barlow writes that Mr. Fitzgerald-Carrier estimates that the largest decile of U.S. stocks account for 76.2 per cent of the S&P 500, a new record. The Magnificent Seven still account for a third of the S&P 500 despite Tesla's 22-per-cent decline and Apple's 17-per-cent drop year-to-date. A U.S. technology sector swoon will take Canadian tech stocks with it. The Toronto Stock Exchange does not have anything like the tech concentration U.S. markets enjoy, but Shopify remains the second-largest company in the domestic benchmark behind RBC. Shopify, Constellation Software, CGI and Celestica add up to a not-insignificant 8.3 per cent of the S&P/TSX composite. In the event of a drastic correction in global technology stocks, the TSX will have a hard time overcoming the drag presented by these companies. Calling market tops remains a tough game. Meanwhile, Mr. Barlow says he is being careful to avoid excess risk in his portfolio by keeping the beta -- sensitivity to market movements -- below 1.0 by emphasizing non-technology stocks.