President Trump's tariffs on US steel and aluminum imports went into effect on March 23, with exceptions for certain countries. As of March 28, the tariffs apply to one-third of steel and 45 percent of aluminum imports. The list of countries affected has been changing since February, with no timeline or explicit criterion for the removal of the restrictions. The tariffs were invoked under a controversial legal justification that these imports threaten American national security.
This PIIE Chart was adapted from Chad P. Bown's blog post, Trump's Long-awaited Steel and Aluminum Tariffs Are Just the Beginning.