资料：You can not go forward by going backward. Take the current debate about trade and globalization, for instance, while the impulse to erect trade barriers is understandable given the pain experienced in recent years, it is not the way to create lasting growth and shared prosperity. Over the past three decades, global flows of trade and investment have accelerated dramatically, creating enormous economic value. However, trade and globalization have also brought wrenching job losses. The financial crisis and weak recovery have made matters worse, intensifying the backlash against trade and globalization. Part of the problem is that the benefits of trade and investment go largely unrecognized, while the job losses are often overstated. Another significant problem is that participation in trade and investment is limited to a relatively small set of firms. In the U.S., large firms account for three-quarters of total exports, and the vast majority of small and medium-size businesses do not export. This means firms have a great opportunity to boost growth and productivity through wider participation in trade. That leaves the question of how to help those hurt by trade and globalization. Too often we talk about re-training as a panacea（万能药）.And yes, it helps. But it needs to take into account the different requirements of each workforce and needs to be part of a wider set of support for affected workers and communities. Above all, it is important to recognize that our economic transition to a global and digital economy is an irreversible trend. Only by broadening participation in the global economy, rather than by trying to turn back the clock, will we discover answers to today’s most vexing economic problems. What is the MAIN opinion expressed in the opening paragraph?