Weekly average prices of the Organization of Petroleum Exporting Countries (OPEC) dropped slightly to 105.17 U.S. dollars per barrel last week, the Vienna-based cartel said Monday. This is the third consecutive week of decline, which has recorded the lowest price since August. The global economic weakness, together with the European debt crises and slowdown in China\'s economy are reducing the world oil demand expectation, OPEC said in its latest report. OPEC\' latest annual report cut its medium-term and long-term global oil demand forecast. Meanwhile, the organization also lowered its forecast for global oil demand in 2013 in a monthly report last Friday.