There are worse economic trends than slowing productivity. How about declining productivity for one? That’s the nasty trick pulled by the US construction sector. It’s been running in reverse for a half-century while the rest of the economy sped ahead. A new Richmond Fed study, “Five Decades of Decline: U.S. Construction Sector Productivity,” finds labor productivity in construction has fallen more than 30 percent since 1970. Over the same half-century, overall US productivity doubled.