The Globe and Mail reports in its Friday edition North American indexes suffered triple-digit losses on Thursday, just a day after the Commerce Department reported better-than-expected U.S. economic growth of 4 per cent in the second quarter, annualized. The Globe's David Berman writes that in Canada, GDP grew 0.4 per cent in May, also topping expectations. Yet stocks suffered one of their worst one-day drubbings of the year. The blue-chip Dow Jones industrial average tumbled 317.06 points or 1.9 per cent, to 16,563.30. The broader S&P 500 fell 2 per cent. Canada's S&P/TSX composite index fell 194.08 points, or 1.25 per cent, to 15,330.74. There are some concerns hanging over the stock market. For one, steady improvements in U.S. economic growth and employment come with a catch: They put pressure on the Federal Reserve to raise ultralow interest rates. For another, stocks have been enjoying an unusually long streak of steady gains. The S&P 500 has gone three years without a correction of 10 per cent or more, lifting it to record highs in July but also raising the likelihood of a setback. Fed chair Janet Yellen recently warned of some "stretched" valuations in the stock market.