1973, Venezuela voted to nationalize its oil industry outright, effective 1 January 1976, with Petróleos de Venezuela (PDVSA) taking over and presiding over a number of holding companies; in subsequent years, Venezuela built a vast refining and marketing system in the U.S. and Europe. In the 1990s PDVSA became more independent from the government and presided over an apertura (opening) in which it invited in foreign investment. Under Hugo Chávez a 2001 law placed limits on foreign investment. The state oil company PDVSA played a key role in the December 2002 – February 2003 national strike which sought President Chávez' resignation. Managers and skilled highly paid technicians of PDVSA shut down the plants joined the strike, and petroleum production and refining by PDVSA almost ceased. Activities eventually were slowly restarted by returning and substitute oil workers. As a result of the strike, around 40% of the company's workforce (around 18,000 workers) were dismissed. Transport Venezuela is connected to the world primarily via air (Venezuela's airports include the Simón Bolívar International Airport in Maiquetía, near Caracas and La Chinita International Airport near Maracaibo) and sea (with major sea ports at La Guaira, Maracaibo and Puerto Cabello). In the south and east the Amazon rainforest region has limited cross-border transport; in the west, there is a mountainous border of over shared with Colombia. The Orinoco River is navigable by oceangoing vessels up to inland, and connects the major industrial city of Ciudad Guayana to the Atlantic Ocean. Venezuela has a limited national railway system, which has no active rail connections to other countries. The government of Hugo Chávez tried to invest in expanding it, but Venezuela's rail project is on hold due to Venezuela not being able to pay the $7.5 billion and owing China Railway nearly $500 million. Several major cities have metro systems; the Caracas Metro has been operating since 1983. The Maracaibo Metro and Valencia Metro were opened more recently. Venezuela has a road network of nearly in length, placing the country around 45th in the world; around a third of roads are paved. Demographics Venezuela is among the most urbanized countries in Latin America; the vast majority of Venezuelans live in the cities of the north, especially in the capital Caracas, which is also the largest city. About 93% of the population lives in urban areas in northern Venezuela; 73% live less than from the coastline. Though almost