Can pure business-owner optimism translate into economic acceleration? Next year may offer the ultimate test of that proposition in America, as Donald Trump and his aides take the reins for a second time.

They have been shopping the narrative that lower taxes, reduced federal regulation and a trade policy that emphasizes domestic production will generate a stronger economy that lifts all boats. Even the giant US fiscal deficit won’t be such a problem as a bigger GDP shrinks the relative burden, they contend. Anyone acquainted with Reaganomics may be familiar with this theory.