Tariffs have been applied over the years to protect homegrown industries and target competitors who are seen as using unfair trade practices. They impose costs on both importers and exporters and had been in decline until the recent U.S.-China trade war.

Responsible for powering the country and its economy, the U.S. energy grid has come under increasing strain due to climate change, and the threat of cyberattacks looms.  

World powers continue to punish North Korea with economic sanctions, but the pressure has so far failed to push Pyongyang toward denuclearization.

With economic inequality at an all-time high, some U.S. presidential candidates are proposing dramatic shifts to the U.S. tax code. How have similar plans worked elsewhere in the world?