Houston is a diverse and international city, in part because of its many academic institutions and strong biomedical, energy, manufacturing and aerospace industries. According to the U.S. Census 2000, the racial makeup of the city was 49.3% White (including Hispanic or Latino), 25.3% Black or African American, 0.4% Native American, 5.3% Asian, 0.1% Pacific Islander, 16.5% from other races, and 3.2% from two or more races. 37% of the population was Hispanic or Latino of any race. By 2010 Houston had significant numbers of Hispanic and Latino Americans, African Americans, Chinese Americans, and Indian Americans, as well as the second-largest Vietnamese-American population of any U.S. city. The city of Houston became a "majority-minority" city (one where the non-Hispanic White population is smaller than the other minority groups combined) in the 1990s, and by 2000 the total Greater Houston area also became a majority-minority. John B. Strait and Gang Gong, authors of the journal article "Ethnic Diversity in Houston, Texas: The Evolution of Residential Segregation in the Bayou City, 1990–2000", wrote that in the 1990s, the minority groups of Houston became more integrated with one another but more segregated from whites. Hispanics integrated with other groups more because the overall number of Hispanics in Greater Houston increased. Many Asians moved into neighborhoods with other Asians, and blacks and Hispanics moved into neighborhoods which Whites were leaving. Hispanics and Latinos The Hispanic population in Houston is increasing as more immigrants from Latin American countries come to work in the area. As of 2006 the city has the third-largest Hispanic population in the United States. As of the same year Karl Eschbach, a University of Texas Medical Branch demographer, said that the number of illegal immigrants in the Houston area was estimated at 400,000, with over 70% being of Mexican descent. This influx of immigrants is partially responsible for Houston having a population younger than the national average. As of 2011, the city is 44% Hispanic. As of 2011, of the city's U.S. citizens that are Hispanic, half are at voting age or older. Many Hispanics in Houston are not U.S. citizens, especially those living in Gulfton and Spring Branch. As a result, Hispanics have proportionally less representation in the municipal government than other ethnic groups. As of April 2011 two of the Houston City Council members are Hispanic, making up 18% of the council. As of 2010, Strait and Gong, authors of