strengthening the city's role as a transportation center. The opening of the Georgia World Congress Center in 1976 heralded Atlanta's rise as a convention city. Construction of the city's subway system began in 1975, with rail service commencing in 1979. Despite these improvements, Atlanta lost more than 100,000 residents between 1970 and 1990, over 20% of its population. At the same time, it developed new office space after attracting numerous corporations, with an increasing portion of workers from northern areas. 1996 Summer Olympic games Atlanta was selected as the site for the 1996 Summer Olympic Games. Following the announcement, the city government undertook several major construction projects to improve Atlanta's parks, sporting venues, and transportation infrastructure; however, for the first time, none of the $1.7 billion cost of the games was governmentally funded. While the games experienced transportation and accommodation problems and, despite extra security precautions, there was the Centennial Olympic Park bombing, the spectacle was a watershed event in Atlanta's history. For the first time in Olympic history, every one of the record 197 national Olympic committees invited to compete sent athletes, sending more than 10,000 contestants participating in a record 271 events. The related projects such as Atlanta's Olympic Legacy Program and civic effort initiated a fundamental transformation of the city in the following decade. Since the 21st century During the 2000s, the city of Atlanta underwent a profound physical, cultural, and demographic change. As some of the African American middle and upper classes also began to move to the suburbs, a booming economy drew numerous new migrants from other cities in the United States, who contributed to changes in the city's demographics. African Americans made up a decreasing portion of the population, from a high of 67% in 1990 to 54% in 2010. From 2000 to 2010, Atlanta gained 22,763 white residents, 5,142 Asian residents, and 3,095 Hispanic residents, while the city's black population decreased by 31,678. Much of the city's demographic change during the decade was driven by young, college-educated professionals: from 2000 to 2009, the three-mile radius surrounding Downtown Atlanta gained 9,722 residents aged 25 to 34 and holding at least a four-year degree, an increase of 61%. This was similar to the tendency in other cities for young, college educated, single or married couples to live in downtown areas. Between the mid-1990s and 2010, stimulated by funding from the HOPE VI program and under