During his inaugural speech, US President Donald Trump threatened to "take back" the Panama Canal. Built by the US in the early 20th century, the waterway is a key maritime trade route. The US relinquished control of it back in 1999 in a deal that obliged the operator to charge ships fairly. We take a closer look at the economy behind the canal. Plus, Trump is promising to significantly change US trade policy through tariffs. But do these taxes protect domestic jobs and workers?