yes, back in the old days they used to measure an economy by tons shipped. It doesn't apply anymore due to higher value things being lighter, and tracking air-

yes, back in the old days they used to measure an economy by tons shipped. It doesn't apply anymore due to higher value things being lighter, and tracking air-shipments would be a problem. However, it does underlie a point - tracking the value of shipments by a currency value can easily obscure important facts.