What is the main idea of this passage? [br] [originaltext]A libertarian think t

A libertarian think tank, reckon that eliminating all travel visas to the United States would add between $90 billion and $123 billion in annual tourist spending. By one estimate, introducing visa restrictions can lower trade and foreign direct investment between a pair of countries by as much as 25% .

Trade, though, has an acute image problem. Its benefits are hard to perceive directly, spread as they are across large constituencies: consumers, exporters, and workers who may not realize just how much of what they make is shipped overseas. Cheap imports have been lethal for many American manufacturers, particularly in the mid-western rust-belt and in the South.