The wood was in the import number and the screwdriver was in the GNP number.
Lets say wood is 16% of the cost of the screw driver. (Coincidently the same porportion as tariffs to GNP). And let’s say the screw driver costs $1.00 to produce pre-tariff and the wood costs $0.16 to import. We increase the cost of the wood by 10% so it now costs $0.176. Nothing else changes, so the cost to produce the screwdriver is $1.016, a 1.6% increase.
“The curious task of economics is to demonstrate to men how little they really know about what they imagine they can design.”
― Friedrich von Hayek