But there is more to the productivity conundrum than the 2008 crisis. In the two decades that preceded the crisis, the sector of the US economy that produces internationally tradable goods and services – one-third of overall output – failed to generate any increase in jobs, even though it was growing faster than the non-tradable sector in terms of value added.
但生产率之谜并不只是在2008年危机后才出现。在危机前的二十年中，美国经济中生产国际可贸易商品和服务（占总产出的三分之一）的部门没有增加任何就业岗位，即使用增加值衡量，其增长比不可贸易部门更快。