What’s behind the global stock market selloff?

By David Randall and David GaffenNEW YORK (Reuters) – Global stock markets are on their shakiest footing in years.Investors are fleeing stocks and running to safe-havens like bonds and gold, driven by concerns about economic growth the effectiveness of central banks’ policies.At the same time, tumbling energy prices are upending the economies of oil-producing countries, further slicing into global economic growth.Only six weeks ago cheap oil prices were still expected to cushion the