The period of rapid economic growth over the past 50 years was exceptional and will not be repeated without an unprecedented acceleration in productivity growth, according to a new report from the McKinsey Global Institute. The report, Global growth: Can productivity save the day in an aging world?, attempts to clarify long-term growth prospects amid deep uncertainty. It focuses on the 19 national economies in the G20 plus Nigeria, which together account for 63 percent of the world's population and 80 percent of global gross domestic product.