When US President Donald Trump was inaugurated to his second term as president on Jan. 20, oil prices were close to the highs of the summer before. By early May, they had plunged by nearly a quarter.

Oil fell by more than $1 a barrel on Monday to settle at over four-year lows as an OPEC+ decision to expedite its output hikes stoked fears about rising global supply at a time when the demand outlook is uncertain.

Prices have been on the downward trend since early April, when they fell as low as $55 a barrel on the heels of Trump’s tariffs on most countries