According to Roger Noriega, the turbulent period in Latin American was caused by ______.

State Department officials say there will be no changes in current U.S. policy towards Latin America after Assistant Secretary of State for Western Hemisphere Affairs Roger Noriega steps down on September 16. Since his Senate confirmation in July 2003, Mr. Noriega has presided over some successes - such as the recent congressional ratification of the Central American Free Trade Agreement - but also has had to deal with a particularly turbulent period in Latin American politics. Mr. Noriega tells VOA weak democratic institutions are responsible for instability in some Latin American countries. Since late 2003, several elected presidents have been forced out of office in the face of popular unrest. In February 2004, Haitian President Jean Bertrand Aristide resigned and fled his country, following an armed uprising. His departure led to the intervention in Haiti of a multinational force to stabilize the Caribbean nation. In April of this year, Ecuador’s Congress dismissed President Lucio Gutierrez following violent demonstrations over his economic and political policies. In June, Bolivian President Carlos Mesa was also forced out of office. He said he could no longer govern in the face of continuing protests demanding nationalization of Bolivia’s energy industry. As vice president in October 2003, Mr. Mesa had replaced President Gonzalo Sanchez de Lozada, a free market advocate who had also resigned in the face of mass demonstrations and strikes.