From the days of the Aztecs, Mexico City has been the center of power for much of Mesoamerica and the Mexican nation. This centralism simply changed hands when the Spanish arrived, The Institutional Revolutionary Party (PRI), which came to power after the Mexican Revolution, again consolidated political power to the city, which benefited to the detriment of other parts of the country. The rapid expansion of Mexico City is related to the country's economic development in the period after World War II, the widening of the manufacturing sector, the success of the oil industry, and the country's proximity to U.S. markets. This growth allowed for the tolerance of PRI's authoritarianism. It still experienced economic growth up to the 1960s, but problems brought on by the one-party system were beginning to show. In 1968, Mexico City hosted the Summer Olympic Games. The event was meant to signal the prosperity of a developing nation, but serious problems had been masked by the PRI's authoritarian regime. Shortly before the inauguration of the Games, government troops massacred an unknown number of protesting students in Tlatelolco. However, the last straw may have been the 1985 Mexico City earthquake. On Thursday, 19 September 1985, at 7:19 am local time, Mexico City was struck by an earthquake of magnitude 8.1. on the Richter magnitude scale. The event caused between three and four billion USD in damage as 412 buildings collapsed and another 3,124 were seriously damaged in the city. While the number is in dispute, the most-often cited number of deaths is about 10,000 people.