The most damaging occurrence to ever affect the trade relationship between Saudi Arabia and the U.S. occurred on September 11, 2001 due to Saudi Arabia's believed involvement in the 9/11 attacks that occurred in multiple cities throughout the United States. Tensions also rose between the two nations throughout Barack Obama's presidency due to the United States agreement in the Iran, when the U.S. removed oil sanctions on Iran and allowed them to sell their oil to the U.S. The relationship was also hindered by the oil market crash of 2014, propelled by increased shale oil production in the United States, which in turn caused Saudi Arabian exports of oil to decrease by nearly fifty percent. Oil went from around $110 a barrel prior to the 2014 crash, to about $27 a barrel by the beginning of 2016. This relationship worsened after the U.S. legislation passed a bill of a that allowed victims of the 9/11 attacks to sue the Saudi Arabian government for their losses in 2016.